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BIOLOGY 

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A  LABORATORY   MANUAL  OF 

INVERTEBRATE 
ZOOLOGY 


BY 

OILMAN  A.  DREW,  PH.D. 

ASSISTANT    DIRECTOR    OF   THE    MARINE   BIOLOGICAL    LABORATORY, 
WOODS   HOLE,    MASSACHUSETTS 


WITH  THE  AID  OF 

FORMER  AND  PRESENT  MEMBERS  OF  THE 

ZOOLOGICAL  STAFF    OF  INSTRUCTORS    AT 

THE     MARINE    BIOLOGICAL    LABORATORY 

WOODS  HOLE,  MASS. 


SECOND  EDITION, 


PHILADELPHIA  AND  LONDON 

W.  B.  SAUNDERS  COMPANY 

1913 


D7 


2JOUX2X* 

-.  -••;  -'• 

G 


Copyright,  1907,  by  W.  B.  Saunders  Company.     Revised,  reprinted, 
and  recopyrighted  July,  1913 


Copyright,  1913,  by  W.  B.  Saunders  Company 


*N* 


PRINTED     IN     AMERICA 


PRESS      OF 


PHILADELPHIA 


PREFACE  TO  THE  SECOND   EDITION 


THIS  edition  contains  descriptions  for  the  study  of  a  few 
forms  and  a  rather  simple  literature  list  that  were  not  included 
in  the  first  edition.  There  has  been  no  attempt  to  make  the 
literature  list  at  all  complete,  but  it  seems  desirable  to  refer 
students  to  some  of  the  available  papers,  for  by  consulting 
them  in  connection  with  their  laboratory  work  they  become 
acquainted  with  methods  of  work  and  develop  the  spirit  of 
research  that  is  the  beginning  of  real  understanding. 

Certain  text-books  should  be  used  freely  for  reference. 
These  have  not  been  mentioned  under  the  special  heads,  as  they 
apply  to  practically  all  groups.  Among  these  may  be  men- 
tioned Parker  and  HaswelPs  "Text-book  of  Zoology/'  Macmil- 
lan;  Lankester's  "A  Treatise  on  Zoology/'  Black;  Harmer  and 
Shipley's  "The  Cambridge  Natural  History,"  Macmillan; 
Lang's  "Lehrbuch  der  Vergleichenden  Anatomie,"  Fischer;  or 
the  English  translation,  Macmillan;  Korschelt  and  Heider's 
"Lehrbuch  der  Vergleichenden  Entwicklungsgeschichte/'  Fis- 
cher; or  the  English  translation,  Macmillan;  and  Delage  et 
Herouard's  "Traite  de  Zoologie  Concrete,"  Schmidt. 

For  the  many  suggestions  and  criticisms  from  zoological 
friends  the  author  is  deeply  grateful.  To  Dr.  Lorande  L. 
Woodruff,  who  has  given  much  attention  to  the  revision  of 
the  Protozoa,  and  to  Dr.  Winterton  C.  Curtis  and  Dr.  Caswell 
Grave,  who,  with  the  men  associated  with  them  as  instructors 
in  the  Zoology  Course  at  the  Marine  Biological  Laboratory, 
have  given  much  attention  to  corrections  and  additions  through- 
out the  manual,  special  acknowledgments  are  due,  for  they  have 
not  only  saved  the  author  much  labor,  but  have  added  mate- 
rially to  the  value  of  the  revision. 

THE  AUTHOR. 

July,  1913. 

iii 


313810 


PREFACE. 


THE  present  manual  has  for  its  basis  a  set  of  laboratory  direc- 
tions prepared  by  members  of  the  staff  of  instructors  to  meet 
the  needs  of  the  class  in  general  zoology  at  the  Marine  Biolog- 
ical Laboratory  of  Woods  Hole,  Massachusetts.  Those  who 
were  associated  with  me  in  the  preparation  of  the  first  notes 
were  Dr.  Robert  W.  Hall,  Dr.  James  H.  McGregor,  Mr.  Robert 
A.  Budington  and  Dr.  Caswell  Grave.  Other  members  of  the 
staff  who  have  either  aided  me  in  modifying  the  original  notes 
or  who  have  added  others  are  Dr.  Winterton  C.  Curtis,  Dr.  D. 
H.  Tennant,  Dr.  Otto  C.  Glaser,  Dr.  Grant  Smith,  Dr.  John  H. 
McClellan  and  Dr.  Lorande  L.  Woodruff.  Each  year  for  the 
past  six  years  the  directions  have  been  changed  where  experi- 
ences indicated  changes  should  be  made. 

Probably  few  instructors  will  find  it  desirable  for  their  stu- 
dents to  follow  closely  all  that  is  given  in  this  manual,  but  it  has 
seemed  better  to  arrange  the  matter  in  a  logical  order,  and  in 
some  of  the  forms  to  call  attention  to  only  the  important  points 
of  anatomy  or  adaptation,  than  to  try  to  make  the  directions 
for  each  form  complete  in  themselves.  To  make  the  directions 
for  each  form  complete  would  necessarily  add  much  labor  for 
the  student  and  would,  by  the  repetition  of  well-known  facts, 
tend  to  blunt  some  of  the  new  and  important  points  to  be  gained. 

The  type  method  of  laboratory  study  has  for  many  years  been 
the  prevailing  method,  but  care  needs  to  be  exercised  to  keep 
students  from  making  everything  conform  to  type,  and  in  lead- 
ing them  to  see  the  wonderful  adaptations  that  fit  the  different 
animals  for  their  particular  lives.  The  manual  is  not  intended 
to  lead  students  to  a  knowledge  of  comparative  anatomy  alone, 
but  to  an  appreciation  of  adaptation  as  well. 

It  has  fallen  on  me  year  by  year  to  see  that  desirable  changes 
were  made  in  the  directions,  and  it  has  finally  been  my  lot  to 
put  them  into  their  present  form,  but  much  of  the  credit  be- 
longs to  the  men  who  have  been  associated  with  me  in  the 
instruction  work  at  the  Marine  Biological  Laboratory. 

THE  AUTHOR. 


CONTENTS. 


PAOD 

PROTOZOA 1 

RHIZOPODA 3 

Amoeba  proteus 3 

Foraminif  era 5 

Actinosphserium  or  Actinophrys 6 

MASTIQOPHORA 7 

Euglena 7 

Volvox 8 

Ceratium 9 

Noctiluca 0 

SPOROZOA 10 

Gregarina 10 

INFUSORIA 11 

Paramaecium 11 

Spirostomum 12 

Vorticella 13 

Oxytricha 14 

Euplotes 15 

PORIFERA. 17 

Grantia 18 

CCELENTERATA 22 

HYDROZOA 24 

Hydra  (Fresh-water  Polyp) 24 

Obelia 26 

Parypha 28 

Gonionemus 29 

Hydrocorallina 31 

Siphonophora 31 

SCYPHOZOA 32 

Aurelia 32 

ACTINOZOA 34 

Metridium  (Sea-Anemone) 34 

CTENOPHORA 37 

Mnemiopsis 37 

PLATYHELMINTHES 39 

TURBELLARIA 40 

Planaria  maculata 40 

Bdelloura  or  Syncoelidium 41 

TREMATODA 44 

Hsematolcechus  (Distomum) 44 

CESTODA 46 

Crossobothrium  laciniatum . .  46 


Vlll  CONTENTS. 

PLATYHELMINTHES  (Continued).  PAOB 

NEMERTINEA 49 

Tetrastemma 49 

NEMATHELMINTHES 51 

Ascaris 51 

Trichina 52 

TROCHELMINTHES 54 

ROTIFERA 54 

Brachionus  (A  Rotifer) 54 

MOLLUSCOIDA 56 

POLYZOA 56 

Bugula 56 

Plumatella 58 

BBACHIOPODA 58 

Terebratulina 58 

ECHINODERMATA 60 

ASTEROIDEA 61 

Asterias  (Starfish) 61 

OPHIUROIDEA 67 

^    Ophiura  (Serpent-Star) 67 

/ECHINOIDEA 68 

1      _  Strongvlocentrotus  (Sea-Urchin) 68 

HOLOTHUROIDEA ~~'.  .  .  . 74 

Thyone  (Sea-Cucumber) 74 

ANNELIDA 78 

CH^BTOPODA 79 

Nereis  virens  (Clam-Worm) 79 

Lumbricus  (Earthworm) 82 

Autplytus  cornutus 88 

Lepidonotus  squamatus 89 

Diopatra  cuprea 90 

Chsetopterus 90 

Amphitrite  ornata 91 

Cistenides  gouldii 92 

Clymenella  torquata 92 

Arenicola  cristata 93 

Sabella  microphthalma 93 

Hydroides 94 

Spirorbis  borealis 94 

GEPHYREA 95 

Phascolosoma 95 

MOLLUSCA 97 

LAMELLIBRANCHIATA 99 

Venus  mercenaria  (Quahog) 99 

Yoldia  limatula 107 

Mytilus  or  Modiola  (Mussels) 109 

Pecten  irradians  (Scallop) 110 

Ostrea  virginiana  (Oyster) Ill 

Solenomya 112 

Mya  arenaria  (Long  Clam) 112 

Ensis  directus  (Razor-shell  Clam) , 113 


CONTENTS.  IX 


MOLLUSCA  (Continued). 

AMPHINEURA  ...............................................  115 

Chsetopleura  .....  .  .....................................  115 

GASTROPODA  .........................  .  .....................  116 

Fulgur  (Sycotypus)  ..............  .......................  116 

CEPHALOPODA  .............................................  124 

Loligo  pealii  (Squid)  ....................................  124 

ARTHROPODA  ...............................................  133 

CRUSTACEA  ................................................  137 

Homarus  americanus  (Lobster)  ...........................   137 

Callinectea  hastatus  (Blue  Crab)  .........................   144 

Eupagurus  (Hermit  Crab)  ...............................   148 

Hippa  (Sand  Mole)  .....................................   148 

Squilla  ................................................   149 

Mysis  .................................................   151 

Talorchestia  (Beach-Flea)  ...............................  151 

Porcellio  or  Oniscus  (Sow-Bug)  ..........................  152 

Caprella  ...............................................  153 

Branchipus  (Fairy  Shrimp)  ..............................  153 

Daphnia  ...............................................   154 

Cyclops  (Water-Flea)  ...................................  155 

Argulus  (Fish-Louse)  ...................................  156 

Lepas  (Goose-Barnacle)  .................................  156 

ARACHNOIDEA  .............................................  158 

Limulus  (Horseshoe  Crab)  ..............................  158 

Buthus  (Scorpion)  ......................................  159 

Epeira  (Round-Web  Spider)  .............................  160 

Phoxichilidium  .........................................  162 

MYRIAPODA  ................................................   163 

Lithobius  (Centipede,  Earwig)  ...........................  163 

Julus  (Thousand-legs)  ..................................  164 

INSECTA  ...................................................  164 

Acridium  (Grasshopper)  .................................  164 

Apis  mellifica  (Honey-Bee)  ..............................  170 

CHORDATA  ..................................................  174 

UROCHORDA  ...............................................  175 

Dolichoglossus  (Balanoglossus)  ...........................  175 

Molgula  manhattensis  ..................................  176 

Perophora  .............................................  180 

Botryllus  ..............  ................................  180 

Amaro3cium  (Sea-Pork)  .................................  181 

Salpa  cordif  ormis  ......................................  183 

ACRANIA  ..................................................  185 

Amphioxus  lanceolatus  ..................................  185 

NOTES  FOR  GUIDANCE  IN  MAKING  PERMANENT  PREPA- 
RATIONS ..................................................   187 

GLOSSARY  ......................  .............................   193 

INDEX..  .  207 


INVERTEBRATE  ZOOLOGY. 


PROTOZOA* 

Unicellular  Animals. 

CLASS  1.  Rhizopoda. 

With  changeable  pseudopodia  during  adult  life. 
Reproduction  by  simple  division  and  by  spore- 
formation. 

Subclass  1.  Amoebina. 

With  lobose  pseudopodia.  (Amoeba,  Arcella, 
Difflugia.) 

Subclass  2.  Foraminifera. 

With  fine  branching  and  anastomosing  pseudo- 
podia. Shells,  when  present,  usually  calcare- 
ous. (Lecythium,  Globigerina.) 

Subclass  3.  Heliozoa. 

Typically  spherical  in  form.  The  pseudopodia, 
which  radiate  from  the  entire  surface  of  the 
body,  are  ray-like,  seldom  changeable,  and 
usually  possess  an  axial  filament.  (Actino- 
phrys,  Actinosphserium,  Clathrulina.) 

Subclass  4.  Radiolaria. 

With  ray-like  pseudopodia,  and  with  a  chitinous 
capsule  inclosing  the  nuclei.       The  skeleton, 
when  present,  is  formed  of  silica  or  acanthin. 
All  are  marine.     (Thallassicolla.) 
CLASS  2.  Mastigophora. 

Motile  organs  in  the  form  of  flagella.  Repro- 
duction by  longitudinal  division.  Colony  for- 
mation is  frequent. 

Subclass  1.  Flagellidia. 

With  a  definite  anterior  end  on  which  there  are 
one  or  more  flagella.   The  members  of  one  order 
(Choanoflagellida)  have  one  or  more  collar-like 
1  1 


. 


processes  about  the  base  of  the  single  flagellum. 
(Mastigamceba,  Trypanosoma,  Euglena,  Pera- 
nema,  Prpterospongia.) 

Subclass  2.  Dinoflagellidia. 

Usually  with  two  flagella,  one  encircling  and 
the  other  directed  away  from  the  body.  (Peri- 
dinium,  Ceratium.) 

Subclass  3.  Cystoflagellidia. 

With  two  flagella,  one  of  which  is  modified  into 
a  "tentacle,"  while  the  other  is  short  and  con- 
tained within  the  gullet.     (Noctiluca.) 
CLASS  3.  Sporozoa. 

Without  flagella  or  cilia  in  the  adult  period  of 
the  life-cycle.  Reproduction  is  by  spore-form- 
ation. All  are  endoparasites. 

Subclass  1.  Telosporidia. 

Sporulation  phase  of  the  life-cycle  is  distinct 
from  and  follows  the  trophic  phase. 
Order  1.  Gregarinida. 

The  young  stages  are  intracellular  parasites, 
while  the  adults  are  free  and  motile  in  the  di- 
gestive tract  or  body-cavity  of  the  host. 
Sporulation  occurs  within  a  cyst  during  the  free 
period  of  the  life-cycle.  (Gregarina.) 
Order  2.  Coccidiidia. 

Without  a  free  and  motile  adult  stage.     Sporu- 
lation occurs  within  a  cyst  during  the  intra- 
cellular period  of  the  life-cycle.     (Coccidium.) 
Order  3.  Hsempsporididia. 

Living  chiefly  in  the  blood-corpuscles  of  verte- 
brates. In  many  forms  the  entire  sexual 
period  of  the  life-cycle  takes  place  in  an  inter- 
mediate host,  as  the  mosquito.  (Plasmodium.) 

Subclass  2.  Neosporidia. 

Sporulation   takes   place   during   the   trophic 
phase  of  the  life-cycle. 
Order  1.  Myxosporididia. 

The  initial  free  stage  occurs  in  the  tissues  or  the 
cavities  of  the  organs  of  the  host.     The  adult 
form  is  amoeboid.     (Myxidium.) 
Order  2.  Microsporidia. 

Amoeboid  trophozoites.  Spores  very  minute 
and  with  but  one  polar  capsule. 


PROTOZOA. 


3 


Order  3.  Sarcosporidia. 

The  initial  stage  of  the  life-cycle  occurs  in  the 
muscle-cells  of  vertebrates.     (Sarcocystis.) 
CLASS  4.  Infusoria. 

With  motile  organs  in  the  form  of  cilia  during 
all  or  part  of  the  life-cycle.  Nucleus  dimorphic 
(macronucleus  and  micronucleus).  Reproduc- 
tion is  by  simple  transverse  division  or  by  bud- 
ding. 
Subclass  1.  Ciliata. 

With  cilia  throughout  the  life-history. 

Order  1.  Holotrichida. 

The  cilia  are  of  approximately  equal  length  and 
thickness  and  equally  distributed  over  the  body. 
Trichocysts  are  present.  (Prorodon,  Paramse- 
cium.) 

Order  2.  Heterotrichida. 

With  a  uniform  covering  of  cilia,  together  with 
an  "adoral  zone"  formed  of  cilia  fused  into 
membranelles.  (Spirostomum,  Stentor,  Halte- 
ria.) 

Order  3.  Hypotrichida. 

The  cilia  are  limited  to  the  ventral  surface  of  a 
dorso-ventrally  flattened  body.  Cilia  often 
fused  into  cirri,  membranelles,  etc.  (Oxy- 
tricha,  Pleurotricha,  Euplotes,  Stylonychia.) 

Order  4.  Peritrichida. 

More  or  less  bell-shaped  in  form.     Cilia  usually 
reduced  to  those  constituting  the  adoral  zone. 
(Vorticella,  Zoothamnium,  Lichnophora.) 
Subclass  2.  Suctoria. 

Usually  possessing  cilia  only  during  the  embry- 
onic stages  of  the  life-history.  Tentacles 
adapted  for  piercing  and  sucking  are  present. 
(Podophrya,  Ephelota,  Acineta.) 

Blochmann:  Die  Mikroscopische  Tierwelt  des  Siisswassers.    Abt.  1.  Pro- 

tozoa, 1895. 

Biitschli:  Protozoa.     Bronn's  Thierreich,  1889. 
Calkins:  Protozoa,  1901. 

-  :  Protozoology,  1909. 

-  :  Marine  Protozoa  of  Woods  Hole.     Bui.  U.  S.  Fish.  Com.,  1901. 
--  :  The  Scope  of  Protozoology.     Science,  1911. 

Conn:  Fresh  Water  Protozoa  of  Connecticut.     Bui.  State  Nat.  Hist. 
Surv.,  1905. 


d:  PROTOZOA. 

Doflein:  Lehrbuch  der  Protozoenkunde.     3d  Auf.,  1911. 

Edmondson:  Protozoa  of  Iowa.     Davenport  Acad.  Sci.,  1906. 

Hartmann:  Praktikum  der  Protozoologie,  1910. 

Jennings:  Behavior  of  the  Lower  Organisms,  1906. 

:  Old  Age,  Death,  and  Conjugation  in  the  Light  of  Work  on  the  Lower 

Organisms.     (Harvey  Lectures),  Pop.  Sci.  Mo.,  1912. 
Kent:  Manual  of  the  Infusoria,  1881. 
Lankester:  Treatise  on  Zoology.     1.  Protozoa. 
Leidy:  Fresh  Water  Rhizopods  of  North  America,  1879. 
Minchin:  Protozoa,  1912. 
Prowazek:  Einfuhrung  in  die  Physiologic  der  Einzellgen  (Protozoen),  1910. 

:  Taschenbuch  der  Mikroskopischen  der  Protistenuntersuchen,  1907. 

Stokes :  Contribution  Toward  a  History  of  the  Fresh  Water  Infusoria  of  the 

United  States.     Jour.  Trenton  Nat.  Hist.  Soc.,  1,  1888. 
Whipple:  Microscopy  of  Drinking  Water,  2d  ed.,  1910. 
Woodruff:  Observations  on  the  Origin  and  Sequence  of  the  Protozoan 

Fauna  of  Hay  Infusions.     Jour.  Exp.  Zool.,  12,  1912. 


RHIZOPODA. 

AMOEBA  PROTEUS. 

Amoebae  are  usually  easily  discernible  under  the  low  power  of 
the  microscope  as  irregular,  semi-transparent,  granular  bodies. 
Find  a  specimen  in  the  material  provided,  which  is  known  to  con- 
tain amoebae,  and  determine  the  following  points: 

1.  With  the  high  power  observe  the  peculiar  method  of  loco- 
motion, the  constant  but  slow  change  in  the  shape  of  the  body 
by  means  of  projections,  pseudopodia,  or  "false  feet." 

Make  sketches  at  intervals  of  one  or  two  minutes  to  show  the 
changes  in  the  form  of  the  body. 

2.  Observe  the  peripheral  zone  of  hyaline  protoplasm,  the 
ectoplasm,  and  compare  this  with  the  inner  protoplasm,  the  endo- 
plasm.    Observe  in  detail  the  formation  of  a  pseudopodium. 
Does  the  endoplasm  extend  into  the  pseudopodium?    Can  you 
explain  how  the  movement  is  caused? 

3.  Find  a  clear  space  which  appears  and  disappears  at  inter- 
vals;   this  is  the  contractile  vacuole.     Determine  the  length  of 
time  between  successive  contractions.    Are  the  intervals  regu- 
lar?   When  the  vacuole  contracts  what  becomes  of  the  con- 
tents?   What  is  its  function? 

4.  Note  the  oval  or  rounded  nucleus  moving  with  the  flowing 
endoplasm.    What  is  its  structure? 


THE    FOBAMINIFERA.  5 

5.  Food  materials  in  process  of  digestion  are  readily  seen. 
Of  what  do  they  consist?  They  are  contained  in  gastric  vacu- 
oles.  By  careful  watching,  it  is  often  possible  to  observe  the  man- 
ner in  which  food  is  ingested  and  the  manner  in  which  the  undi- 
gested matter  is  egested. 

Make  a  careful  drawing  of  an  Amoeba. 

AmoebaB  of  various  kinds  represent  in  many  respects  the 
simplest  type  of  protozoan,  and  are  therefore  placed  in  the  first 
class  of  these  animals,  the  Sarcodina.  The  individuals  of  this 
class  all  possess  pseudopodia,  but  many  are  quite  unlike  those  of 
Amoeba.  Look  over  the  figures  of  various  Rhizopoda. 

If  time  and  material  permit,  study  Amoeba  verrucosa,  Arcella, 
and  Difflugia,  and  compare  them  with  Amoeba  proteus.  Do  you 
understand  how  the  shells  of  the  last  two  genera  are  made,  and 
of  what  service  they  are?  Why  are  not  shells  good  for  all  forms? 

Drawings  of  these  forms  are  desirable. 

Calkins:  The  Fertilization  of  A.  proteus.     Biol.  Bui.,  13,  1907. 
Bellinger :  Locomotion  of  Amoeba  and  Allied  Forms.  Jour.  Ex.  Zool.,  3, 1906. 
Metcalf :  Amoeba  Studies.     Jour.  Ex.  Zool.,  9,  1910. 
Mast:  Reactions  in  Amoeba  to  Light.     Jour.  Ex.  Zool.,  9,  1910. 
Popoff:  Ueber  den  Entwicklungs  cyclus  von  A.  minuta.    Arch.  f.  Protist., 
22,  1911. 

THE   FORAMINIFERA. 

With  very  few  exceptions  Foraminif era  are  marine  and  pro- 
vided with  shells.  Empty  shells  from  deep-sea  dredgings  or  from 
the  sand  beaches  of  such  islands  as  the  Bermudas  may  be  had 
for  study.  Examine  them  with  a  low  power  by  reflected  light. 

1.  Carefully  examine  various  shells,  compare  them  with  each 
other  and  with  figures.    Notice  the  great  variety  in  size  and 
shape  and  determine  how  the  chambers  must  have  been  added 
during  growth. 

2.  Observe  a  single  opening  in  a  shell,  and  determine  whether 
the  general  surface  has  any  finer  perforations.     Be  sure  to  under- 
stand the  relation  of  the  live  animal  to  the  shell. 

Make  drawings  of  several  types  of  shells. 

Farmer:  Foraminif  era,  pp.  133-139,  Lankester's  Treatise. 
Flint:  Recent  Foraminif  era.     Rep.  U.  S.  Nat.  Mus.,  1897. 


PROTOZOA. 


ACTINOSPHAERIUM  OR  ACTINOPHRYS. 

Find,  as  usual,  with  the  low  power,  and  increase  the  magni- 
fication as  occasion  demands. 

1.  Note  the  many  fine  radiating  pseudopodia.    These  are  quite 
stiff  compared  with  those  of  Amceba  and  for  a  considerable  time 
show  little  change,  not  being  pushed  out  and  retracted  constantly 
as  in  Amceba.    Is  the  animal  flat  or  spherical  ? 

2.  Both  ectoplasm  and  endoplasm  are  so  filled  with  vacuoles 
that  they  present  a  frothy  appearance  characteristic  of  most 
Heliozoa.    The  endoplasm  of  all  Protozoa  is  alveolar  in  struc- 
ture, but  in  Actinosphaerium  the  vacuoles  are  exceptionally 
large,  though  not  as  large  as  those  in  the  ectoplasm.     In  Ac- 
tinophrys  the  endoplasm  is  not  so  sharply  separated  from  the 
ectoplasm. 

3.  The  nucleus  of  Actinophrys  is  present  in  the  center  of  the 
organism,  but  it  is  somewhat  difficult  to  demonstrate  in  the  live 
animal.     In  Actinosphaerium  there  are  many  nuclei. 

4.  At  some  point  near  the  periphery,  the  contractile  vacuole 
can  usually  be  seen.     When  it  is  found  notice  its  action,  and 
immediately  after  it  has  contracted  look  among  the  pseudopodia 
of  that  region  for  indications  of  its  extruded  contents. 

Draw  a  specimen,  indicating  all  of  the  points  observed. 

5.  When  the  contractile  vacuole  discharges,  or  when  any 
foreign  body  touches  the  ends  of  the  pseudopodia,  notice  the 
way  in  which  this  type  of  pseudopodium  is  moved.     What  does 
this  indicate  in  regard  to  its  structure?    How  far  do  the  pseudo- 
podia extend?    They  may  be  seen  to  contain  minute  granules 
when  studied  with  the  high  power  and  best  light. 

6.  If  possible,  observe  the  process  of  catching  food  with  the 
tips  of  the  pseudopodia  and  the  manner  in  which  it  is  drawn 
toward  the  body.     Note  any  motion  on  the  surface  of  the  body 
as  the  food  is  drawn  closer,  and  also  the  manner  in  which  the 
food  is  finally  ingested.    Are  there  any  indications  that  the 
pseudopodia  extend  as  still  finer  filaments  beyond  the  point  to 
which  it  is  possible  to  trace  them  with  the  highest  magnifica- 


EUGLENA.  7 

tion  at  hand?  If  the  capturing  of  food  is  observed,  make  a 
series  of  diagrams  to  illustrate  the  process. 

If  possible,  observe  a  specimen  undergoing  division.    Draw. 

It  is  desirable  to  examine  Clathrulina,  noting  the  stalk  and 
skeleton.  Look  over  figures. 

R.  Hertwig:  Ueber  die  Kernteilung,  Richtungskorperbildung  und  Befruch- 
tung  bei  Actinosphserium.  Abt.  d.  Math.  Phys.  Kl.  d.  Ak.  d.  Wiss., 
Miinchen,  19,  1898. 

HASTIGOPHORA. 

EUGLENA. 

Understand  its  habitat  and  with  what  forms  it  is  usually 
associated. 

1.  Observe  the  free-swimming  movements  of  the  organism, 
and  the  euglenoid  changes  in  the  form  of  the  body. 

Make  drawings  showing  the  changes  in  the  shape  of  a  single  in- 
dividual. 

2.  Distinguish   anterior  and  posterior  ends.     Is  there  any 
dorso- ventral  differentiation?    Note  the  motile  organ,  the  flagel- 
lum.     Where  is  it  attached?    What  relation  does  it  bear  to  the 
gullet?    How  is  it  directed  during  locomotion  of  the  organism. 
Does  it  serve  any  other  purpose  besides  locomotion?     (See 
Doflein,  pp.  604,  33  and  207.) 

3.  The  green  color  of  Euglena  is  due  to  chlorophyl,  and  this 
enables  it  to  live  in  clear  water,  being  nourished  like  a  typical 
green  plant.     (See  Minchin,  p.  14.) 

4.  Note  the  absence  of  color  near  the  anterior  and  posterior 
ends  of  the  organism.     Near  the  anterior  end  also  notice  the  red 
pigment  spot,  or  stigma.     What  is  its  probable  function? 

5.  Stain  a  specimen  with'iodin  and   look  for  the  nucleus. 
It  is  obscured  by  the  chlorophyl. 

6.  Observe  specimens  in  the  resting  stage. 
Make  a  drawing  showing  all  of  the  points  observed. 

Look  through  the  stock  cultures  for  other  forms  of  Masti- 
gophora,  such  as  Trachelomonas,  Peranema,  Phacus,  etc. 
It  is  desirable  to  make  drawings  of  the  different  forms. 


8  PROTOZOA. 

Klebs:  Ueber  die  Organisation  einiger  Flagellatengruppen  und  ihre  Be- 
ziehungen  zu  Algen  und  Infusorien.  Unt.  Bot.  Inst.  Tubingen,  1,  1883. 

:  Flagellatenstudien.     Zeit  f.  Wiss.  Zool.,  55,  1893. 

Wager:  On  the  Effect  of  Gravity  upon  the  Movements  and  Aggregation  of 
Euglena  viridis  and  Other  Micro-organisms.  Phil.  Trans.  Roy.  Soc., 
London,  Series  B,  201,  1911. 


VOLVOX. 

Volvox  globator  is  better  for  study  than  V.  aurens.  It  may 
be  distinguished  from  the  latter  by  the  larger  size  of  the  colony, 
the  greater  number  of  cells  that  compose  it  (about  15,000),  the 
angular  shape  of  the  individual  cells,  and  the  stout  connecting 
processes  of  protoplasm,  into  which  chromatophores  may  enter. 

Observe  the  movements  of  colonies  in  a  watch-glass  of  water, 
with  the  naked  eye  and  with  a  low  power  of  the  microscope. 

1.  Do  the  colonies  tend  to  collect  toward  a  particular  side 
of  the  dish?    What  reason  is  there  for  the  reaction? 

2.  Place  a  number  of  colonies  on  a  slide  with  enough  water 
to  allow  them  to  be  covered  without  crushing  them.     Study 
first  with  the  low  and  then  with  the  high  power  and  determine 
the  species.    Understand  the  relation  of  the  individual  cells  to 
the  colony.     (See  Doflein,  p.  222.) 

Draw  a  figure  showing  several  cells  and  their  protoplasmic  con- 
nections. 

3.  Compare  in  detail  an  individual  cell  with  Euglena. 

4.  Observe,  if  possible,  certain  cells,  called  parthenogonidia, 
which  are  specialized  for  asexual  reproduction.    These  divide  and 
form  the  daughter  colonies,  which  become  detached  and  swim 
in  the  interior  of  the  parent  colony.    They  are  finally  liberated 
by  the  rupture  of  the  wall  of  the  parent  colony. 

Make  a  figure  of  a  parent  colony  that  incloses  several  daughter 
colonies  of  different  sizes. 

5.  V.  globator  is  monoecious.    Look  for  eggs  and  bundles  of 
spermatozoa. 

Figure  them. 

6.  Be  sure  to  recognize  the  significance  of  the  fact  that  the 
cells  of  Volvox  are  differentiated  into  somatic  and  germ  cells, 


CERATIUM.      NOCTILTJCA.  9 

and  to  understand  the  resulting  physiological  division  of  labor. 
(See  Calkins,  Protozoa,  p.  232.) 

7.  Consider  the  reasons  for  and  against  regarding  Volvox 
and  allied  organisms  as  animals  rather  than  plants. 

Meyer:  Ueber  den  Bau  von  V.  aurens  und  V.  globator.    Bot.  Cent..  63. 
1895. 


CERATIUM. 

1.  Examine  this  form  with  a  high  power,  and  in  a  favorable 
specimen  notice  the  sculptured  outer  surface  of  the  cellulose 
test.     The  living  animals  are  green  or  brown  owing  to  the  pres- 
ence of  chromatophores  in  the  protoplasm. 

2.  Note  the  furrow  encircling  the  body.     Does  it  extend 
completely  around  it?    Is  there  a  short  furrow  on  one  side  at 
right  angles  to  the  first,  or  a  depression  of  considerable  size? 
Understand  the  position  of  the  flagella. 

Draw  the  animal,  showing  the  points  observed. 

Look  for  examples  of  the  earlier  stages  of  division,  and  of 
later  stages,  which  appear  as  chains  of  fully  formed  individuals 
attached  together. 

Kofoid:  Mutations  in  Ceratium.     Bui.  Mus.  Comp.  Zool.,  52,  1909. 

NOCTILUCA. 

If  living  specimens  are  not  to  be  had  for  study,  material 
preserved  in  alcohol,  after  suitable  fixation,  can  be  used.  Spec- 
imens are  best  examined  in  a  cell-slide  under  a  cover-glass. 

1.  Observe  the  nearly  globular  shape,  and  on  one  side  a  groove 
from  which  arises  a  large  flagellum  or  "  tentacle."     Is  there  a  deep 
groove  near  it  ?    At  the  bottom  of  this  groove  it  is  possible  to  see 
the  mouth  in  a  living  specimen.     Another  smaller  flagellum  is 
visible  in  living  specimens  inserted  at  the  bottom  of  the  mouth, 
but  in  preserving  the  organism  it  is  usually  destroyed. 

2.  Note  the  appearance  of  the  preserved  protoplasm.     The 
endoplasm  appears  parenchymatous.    At  one  point  a  more  com- 


10  PROTOZOA. 

pact  mass  is  seen,  from  which  strands  appear  to  radiate.  This 
has  been  found  to  contain  the  nucleus. 

Noctiluca  is  phosphorescent,  and  frequently  causes  very  bril- 
liant displays. 

Make  a  drawing. 

Calkins:  Nuclear  Division  in  Noctiluca.    Jour.  Morph.,  15,  1899. 


SPOROZOA. 

GREGARINA. 

Remove  the  head  and  posterior  end  of  a  larval  or  adult 
meal  beetle  and  pull  out  the  digestive  tract  with  a  pair  of  for- 
ceps. Place  the  digestive  tract  on  a  slide,  split  it  open  length- 
wise with  a  sharp  scalpel,  and  then  spread  it  out,  with  the 
inner  wall  exposed,  and  cover.  The  operation  should  be  per- 
formed rapidly  to  prevent  the  material  from  drying.  If  the 
beetle  is  infected,  numerous  gregarines  will  be  visible  under  the 
microscope.  Study  with  low  and  high  powers. 

1.  Does  the  animal  move?    A  great  number  of  refractive 
granules  are  present  in  the  protoplasm.     They  are  regarded  as 
reserve  nourishment.     They  can  be  removed  with  acid. 

2.  Note  that  the  body  is  covered  with  a  membrane,  and  is 
divided  into  a  dense  superficial  layer,  the  ectoplasm,  and  a  cen- 
tral, more  fluid  mass,  the  endoplasm. 

3.  The  endoplasm  is  separated  into  two  parts  by  a  portion 
of  the  ectoplasm.     The  anterior  part  is  termed  the  protomerite, 
and  the  posterior  part  the  deutomerite.     In  which  is  the  nucleus 
situated  ? 

4.  Is  it  possible  to  distinguish  a  layer  of  myonemes  just  ex- 
ternal to  the  endoplasm? 

5.  Is  there  another  section  of  the  body  just  anterior  to  the 
protomerite?    If  so,  this  is  the  epimerite. 

6.  Note  that  occasionally  two   (or  more)   individuals  are 
united.     These  aggregations  are  termed  syzygies. 

Before  reproduction  Gregarina  throws  off  the  epimerite, 
leaves  it  in  the  cell-host,  and  falls  into  the  lumen  of  the  digestive 


PARAMLECITJM.  11 

tract.  It  then  encysts,  and  the  protomerite  and  the  deutome- 
rite  form  one  spore-producing  individual.  The  attached  stage 
in  the  life-history  of  Gregarina  is  termed  the  cephalont,  and  the 
detached  stage,  the  sporont.  (See  Calkins'  Protozoa,  Fig.  77.) 
Make  a  drawing. 

Berndt :  Beitrage  zu  Kenntnis  der  im  Darme  der  Larve  von  Tenebrio  moli- 

tor  lebenden  Gregarinen.     Arch  f.  Protist.,  1,  1902. 
Minchin:  Sporozoa,  pp.  177-179,  Lankester's  Treatise. 

INFUSORIA. 
PARAMAECIUM. 

Place  a  drop  of  the  culture  on  a  slide,  cover,  and  examine 
with  the  low  power. 

1.  In  an  animal  not  closely  confined  note  the  shape  and 
movements.     Is  it  possible  to  distinguish  an  anterior  and  a 
posterior  end?    A  forward  and  backward  movement?    Is  one 
side  of  the  animal  kept  constantly  uppermost?    Is  there  a  dorsal 
and  ventral  surface?    Do  the  animals  change  their  shape  either 
permanently  or  temporarily?    Individuals  tend  to  collect  about 
air-bubbles  and  at  the  edge  of  the  cover-glass.     Why? 

Indicate  by  a  sketch  all  the  paints  which  can  be  determined 
with  the  low  power. 

2.  Draw  off  all  superfluous  water  by  means  of  filter-paper, 
add  a  trace  of  powdered  carmine,  and  then  find  a  specimen 
which  is  narrowly  confined  and  examine  it  with  the  high  power. 

The  particles  of  carmine  are  taken  into  the  body.  Deter- 
mine how  and  where.  Note  that  the  carmine  collects  in  gastric 
vacuoles.  What  do  you  think  is  probably  the  nature  of  the 
fluid  in  the  vacuoles?  In  watching  them  do  you  notice  any 
definite  movement  of  the  protoplasm?  Try  to  see  the  undi- 
gested material  ejected. 

3.  Determine  the  arrangement  of  the  cilia,  and  the  nature 
of  their  motion.     Is  there  a  reversal  of  the  direction  of  the  stroke, 
etc.?1 

1  It  is  possible  to  decrease  the  rate  of  movement  of  both  animal  and 
cilia  by  placing  it  in  a  solution  of  gum  arabic.  Specimens  so  treated 
remain  alive  for  some  time. 


12  PROTOZOA. 

4.  Observe  the  contractile  vacuoles.     How  many  are  there? 
Is  their  position  constant?    What  is  their  action?    In  com- 
pressed specimens  the  contractile  vacuoles  and  their  reservoirs 
are  usually  conspicuous.     Note  the  order  of  appearance  and 
disappearance  of  the  vacuoles  and  reservoirs. 

5.  Focus  carefully  on  the  margin  of  the  body  and  note  a  very 
thin  outer  cuticle.    A  thick  layer,  the  ectoplasm,  devoid  of  gran- 
ules but  containing  radially  arranged,  minute,  oval  bodies,  the 
trichocysts,  is  just  internal  to  the  cuticle.     The  inner  mass  of 
protoplasm,   containing  the   contractile   and  gastric   vacuoles, 
and  small  granules,  is  the  endoplasm. 

6.  If  possible  distinguish  the  clear,  centrally  located  nucleus 
(macronucleus). 

Make  a  sketch  showing  all  of  the  above  points. 

7.  Kill  the  animal  by  running  a  drop  of  methyl-green  under  the 
cover-glass.     What  happens  to  the  cilia?    To  the  trichocysts? 

Sketch  the  trichocysts  with  the  threads  protruded,  and  also  note 
and  sketch  the  macronucleus  and  the  micronucleus. 

8.  Observe,  if  possible,  animals  dividing  and  conjugating. 

9.  Study  demonstrations  of  permanently  stained  specimens 
for  finer  structure. 

Calkins  and  Cull:  Conjugation  of  P.  caudatum.     Arch.  f.  Protist.,  10, 1907. 
Jennings  and  Hargitt :  Characteristics  of  the  Diverse  Races  of  Paramsecium. 

Jour.  Morph.,  21,  1910. 
Metalinkow:  Contributions  £  l'6tude  de  la  digestion.     Arch  d.  Zool.  Exp. 

et  Gen.,  9,  1912. 

Schaeffer:  Selection  of  Food  in  Stentor  cseruleus.     Jour.  Ex.  Zool.,  8,  1909. 
Woodruff:    Paramsecium    aurelia    and    Paramsecium    caudatum.     Jour. 

Morph.,  21,  1910. 
:  A  Five  Year  (3000  generations)  Pedigreed  Race  of  Paramsecium 

without  Conjugation.     Proc.  Soc.  Ex.  Biol.  and  Med.,  1912  (also  Biol. 

Centr.,  33,  1913). 

SPIROSTOMUM. 

1.  Compare  Spirostomum  with  Paramaecium,  noting  the 
method  of  locomotion,  the  shape  of  the  body,  the  ciliation,  the 
buccal  groove  and  mouth,  and  the  large  excretory  reservoir,  fill- 
ing the  posterior  end  of  the  body  and  in  communication  with 
the  anterior  end  of  the  body  by  a  canal. 


VORTICELLA.  13 

2.  Note  the  highly  refractive,  long,  band-like  (moniliform) 
macronucleus.     In  another  species  of  Spirostomum  the  macro- 
nucleus  is  similar  to  that  of  Paramsecium.   It  is  desirable  to 
examine  stained  specimens  of  the  two  species  of  Spirostomum. 

3.  Note  the  sudden  contractions  of  the  body.    When  these 
occur  spiral  lines  appear  on  the  surface.     Can  you  distinguish 
these  lines  when  the  animal  is  extended?    These  are  primitive 
structures  (myonemes)  functioning  as  muscles. 

Make  a  drawing  of  the  extended  animal  and  a  diagram  show- 
ing the  form  when  contracted.  (See  Doflein,  p.  968.) 

VORTICELLA. 

Place  a  number  of  individuals  on  a  slide  and  cover  loosely 
to  avoid  crushing.  As  usual,  study  first  with  the  low  power  and 
then  with  the  high. 

1.  Notice  that  the  body  of  Vorticella  has  the  general  shape 
of  an  inverted  bell.     The  covering  of  the  body  is  a  very  thin 
transparent  layer,  the  cuticle,  underneath  which  is  the  periphe- 
ral layer  of  ectoplasm  enveloping  the  more  fluid  and  granular 
endoplasm. 

2.  The  peristome  is  the  rounded  rim  about  the  base  of  the  bell. 

3.  The  elevated  and  inclined  area  included  within  the  peri- 
stome, and  ciliated  around  the  edge,  is  the  disk.     It  is  some- 
what convex. 

4.  The  marked  depression  between  the  disk  and  the  peri- 
stome is  the  vestibule.     It  is  also  lined  with  cilia.    The  vestibule 
defines  the  ventral  surface  of  the  animal. 

5.  The  gullet,  a  slender  canal,  leads  from  the  vestibule  toward 
the  center  of  the  body. 

6.  The  anus  occurs  at  the  side  of  the  vestibule.     It  is  a  tem- 
porary opening  from  which  the  undigested  products  are  passed 
into  the  vestibule  and  so  to  the  exterior. 

7.  Within  the  endoplasm  are  situated  the  clear  contractile 
vacuole,  several  gastric  vacuoles,  the  long  U-shaped  macronucleus, 
and  the  small  round  micronucleus.     The  macronucleus  may  be 
made  more  distinct  by  treating  with  methyl-green. 


14  PROTOZOA. 

8.  The  stalk  is  composed  of  a  sheath,  which  is  continuous  with 
the  cuticle  of  the  body,  and,  within  the  sheath,  the  contractile 
axis  or  myoneme,  which  is  continuous  with  the  body  ectoplasm. 
Notice  that  this  myoneme  is  situated  within  the  sheath  in  a 
very  loose  spiral,  and  that  the  stalk  quickly  contracts  into  a 
close  spiral  when  the  animal  is  stimulated.  Observe  also  the 
manner  in  which  the  peristome  folds  over  simultaneously  with 
the  contraction  of  the  stalk.  What  purpose  does  the  contrac- 
tion of  the  stalk  serve? 

Vorticella  is  distinguished  from  its  allied  genera  by  its  sim- 
ple unbranched  stalk  and  also  by  the  spiral  form  assumed  by  the 
contracted  stalk.  In  which  order  of  the  Ciliata  does  the  cilia- 
tion  of  Vorticella  place  it?  Compare  with  Zoothamnium. 

Make  a  drawing  of  an  expanded  individual  and  a  sketch  to 
show  the  condition  when  contracted.  (See  Doflein,  Fig.  816,  p. 
867.) 

9.  Study,  by  means  of  finely  powdered  carmine,  the  vortex 
currents  set  up  by  the  cilia.     Note  how  the  particles  are  collected 
in  the  gullet,  and  at  intervals  are  forced  in  rounded  masses  into 
the  endoplasm  to  form  gastric  vacuoles.    Is  there  a  definite 
circulation  in  the  endoplasm? 

10.  Endeavor  to  find  several  stages  of  reproduction  by  divi- 
sion. 

Large  fresh-water  species  of  Vorticella  are  preferable  for 
study,  but  marine  species  may  be  substituted  when  necessary. 
If  time  and  material  permit,  study  Lichnophora,  a  marine  peri- 
trichous  form  parasitic  on  Crepidula.  (See  Calkins'  Protozoa, 
p.  203.) 

Schroder:  Beitrage  zur  Kenntnis  von  V.  monilata.    Arch  f.  Protist..  7, 
1906. 

OXYTRICHA. 

Infusoria  belonging  to  the  genus  Oxytricha,  or  the  genera 
Stylonychia,  Pleurotricha,  Euplotes,  etc.  (see  Doflein,  Fig.  136, 
p.  138),  may  be  used  for  the  following  study.  These  forms 
belong  to  the  order  Hypotrichida.  Hypotrichous  forms  are 


ETJPLOTES.  15 

among  the  most  highly  organized  of  the  class  Infusoria,  as  well 
as  of  the  entire  phylum  of  Protozoa,  and  present  a  complexity 
of  structure  and  function  which  is  not  found  probably  within 
the  limits  of  a  single  cell  elsewhere  in  the  animal  series. 

1.  In  an  animal  which  is  becoming  quiet,  note  the  mode  of 
locomotion,  the  shape  of  the  body,  the  buccal  groove,  the  con- 
tractile vacuole,  etc.,  as  in  other  forms  studied.     Compare  the 
dilation  with  that  of  other  forms.    Refer  to  Calkins'  Protozoa, 
Fig.  98,  and  understand  the  relation  of  cirri,  membranelles,  etc., 
to  cilia. 

Draw,  showing  the  structure  in  detail. 

2.  Run  some  methyl-green  under  the   cover-glass.    What 
is  the  shape  of  the  macronucleusf    The  shape  varies  considera- 
bly in  the  different  genera.     Is  it  possible  to  distinguish  the 
micronucleus? 

3.  Prepare  a  fresh  slide  and  observe  in  detail  the  character- 
istic movements  and  manner  of  creeping  over  various  objects. 
As  the  animal  turns  sidewise,  note  the  marked  dorso-ventral 
compression  of  the  body. 

Represent  this  diagrammaticalty  beside  the  previous  drawing. 
It  is  desirable  to  examine  permanently  stained  preparations 
for  division  stages,  finer  details  of  the  nuclei,  etc. 

Wallengren:  Zur  Kenntnis  des  Neubildungs  und  Resorptionsprocess  bei  den 
Teilung  der  Hypotrichen  Infusorien.    Zool.  Jahrb.,  15,  1901. 


EUPLOTES. 

Mount  a  small  piece  of  hydroid  under  a  supported  cover- 
glass  and  with  a  low  power  observe  the  suctorians  attached 
by  delicate  stalks.  Select  a  field  where  the  animals  are  abun- 
dant and  study  under  a  high  power. 

1.  Note  the  general  shape  of  the  cell  and  the  distribution 
of  the  tentacles.  Draw.  Are  all  of  the  tentacles  of  one  kind? 
Observe  the  movements  of  the  tentacles  and  their  use.  Is 
there  any  morphological  relation  between  tentacles  and  cilia? 
(See  Minchin's  Protozoa,  p.  458.) 


16  PROTOZOA. 

2.  Study  the  method  of  exogenous  budding.    What  is  the 
relation  of  this  type  to  simple  division?    Is  the  number  of 
buds  in  process  of  formation  the  same  on  all  specimens? 

3.  Fix,  stain,  and  mount  in  balsam  a  piece  of  hydroid  with 
many  Euplotes  attached.    Under  the  high  power  note  the 
character  of  the  macronucleus  and  its  relation  to  the  buds. 
Are  micronuclei  visible? 

4.  Examine  carefully  the  relation  of  the  stalk  to  the  cell 
body.  '  Compare  with  that  of  Vorticella. 

If  the  material  is  available  study  Podophrya  and  allied 
forms,  with  particular  reference  to  the  method  of  budding. 

Collin:  Etude  monographique  BUT  les  Acine'tiens.    Arch.  Zool.  Exp.  et 
Gen.,  1911  and  1912. 


PORIFERA. 

Cells  not  differentiated  to  form  definite  organs.  Water 
admitted  through  surface  pores  and  ejected  through  an  osculum 
or  through  oscula. 

CLASS  1.  Calcarea. 

With  a  skeleton  composed  of  calcareous  spicules. 

Subclass  1.  Homocoela. 

With  the  gastreal  layer  continuous  sb  the  col- 
lar cells  line  the  whole  gastreal  cavity.  (Leu- 
cosolenia.) 

Subclass  2.  Heterocoela. 

Gastreal  layer  discontinuous.   Collar  cells  restrict- 
ed to  the  flagellated  chambers.     (Grantia.) 
CLASS  2.  Hexactinellida. 

With  a  skeleton  composed  of  siliceous  six-rayed 
spicules. 
Order  1.  Lyssacina. 

Spicules  separate  or  becoming  united.     (Euplec- 
tella.) 
Order  2.  Dictyonina. 

Spicules  united  from  the  first  into  a  firm  frame- 
work.    (Eurete.) 
CLASS  3.  Demospongiae. 

Great  diversity  of  structure.  Dominant  forms 
of  today. 

Subclass  1.  Tetraxonida. 

Typically  with  four-rayed  spicules.     (Corticella.) 

Subclass  2.  Monaxonida. 

Simple,  usually  unbranched  spicules.  Spongin 
frequently  present.  (Cliona,  Suberites,  Chalina, 
Spongilla.) 

Subclass  3.  Keratosa. 

Skeleton  of  spongin  fibers.  No  true  spicules. 
(Euspongia,  Aplysina.) 

Subclass  4.  Myxospongida. 

Without  skeleton.     (Oscarella.) 
2  17 


18  PORIFERA. 

Lankester:  A  Treatise  on  Zoology,  Porifera,  and  Coelenterata,  Pt.  2,  1900. 
Moore:  A  Practical  Method  of  Sponge  Culture.     Bui.  U.  S.  Bur.  Fish.,  28, 

1908. 
:  The  Commercial  Sponges  and  the  Sponge  Fisheries.     Bui.  U.  S.  Bur. 

Fish.,  1908. 
Parker:  The  Reactions  of  Sponges,  with  a  consideration  of  the  Origin  of  the 

Nervous  System.     Jour.  Ex.  Zool.,  8,  1910. 
H.  V.  Wilson:  On  Some  Phenomena  of  Coalescence  and  Regeneration  in 

Sponges.     Jour.  Ex.  Zool.,  5,  1907. 
:  Development  of  Sponges  from  Dissociated  Tissue  Cells.     Bui.  U.  S. 

Bur.  Fish.,  30,  1910. 


GRANTIA. 

This  form  is  quite  common  along  the  New  England  coast, 
where  it  occurs  attached  to. rocks,  seaweeds,  and  submerged 
woodwork  from  just  below  the  lowest  tide-mark  to  a  number  of 
fathoms  in  depth.  You  should  visit  an  old  wharf  where  speci- 
mens may  be  found,  and  study  their  relation  to  the  forms  with 
which  they  are  associated.  Specimens  will  be  found  to  vary 
considerably  in  size.  The  largest  sometimes  reach  an  inch  in 
length. 

1.  Examine  a  dry  specimen  and  notice  its  general  shape, 
manner  of  attachment,  and  osculum.    The  osculum  is  surrounded 
by  a  funnel  of  rather  long  spicules.    Distributed  over  the  gen- 
eral surface,  more  or  less  hidden  by  the  numerous  spicules,  are 
many  small  pores.    Their  presence  may  be  demonstrated  more 
satisfactorily  later. 

2.  Look  for  indications  of  budding.    If  your  specimen  does 
not  show  this,  examine  others. 

Make  an  enlarged  drawing  of  a  sponge. 

With  a  razor  or  sharp  scalpel  cut  a  dry  specimen  into  halves, 
with  a  stroke  from  base  to  osculum,  and  notice : 

3.  The  central  cavity  or  cloaca. 

4.  Many  apopyles,  the  inner  openings  of  tubes  that  are  em- 
bedded in  the  walls  of  the  sponge,  will  be  seen  opening  into 
the  cloaca.    Are  the  apopyles  arranged  in  any  order? 

5.  With  the  low  power  of  your  microscope   (with  the  light 
turned  off)  examine  the  cut  wall  and  find  that  it  is  traversed  by 
parallel  tubes.    Determine  that  these  tubes  are  of  two  kinds. 


GBANTIA.  19 

(a)  Regular,  nearly  cylindrical  tubes  that  open  into  the 
cloaca  through  the  apopyles  and  that  bear  tufts  of  spicules  on 
their  closed  ends,  at  the  surface  of  the  body.  These  are  the 
radial  canals.  It  is  frequently  hard  to  see  their  openings  into 
the  cloaca,  as  the  apopyles  are  narrow,  so  the  section  only  occa- 
sionally passes  through  them. 

(6)  Smaller  and  less  regular  tubes  that  open  on  the  outer 
surface  between  the  clusters  of  spicules,  and  do  not  open  into 
the  cloaca.  These  are  the  incurrent  canals.  In  life  there  are 
small  pores,  prosopyks,  that  open  from  the  incurrent  canals 
into  the  radial  canals.  These  openings  are  very  minute  and  are 
apparently  capable  of  being  closed.  They  are  never  visible 
in  dried  material. 

6.  Examine  thin,  transverse   sections  of  a  dry  sponge  and 
determine  the  positions  of  radial  and  incurrent  canals. 

Make  a  drawing  that  will  show  the  arrangement  of  the  canals. 

7.  Examine  the  spicules  and  determine  their  positions  as 
regards  canals.     Boil  a  portion  of  a  sponge  in  caustic  potash 
until  only  the  spicules  remain  and  examine  the  spicules.    See  if 
more  than  one  kind  occurs. 

Draw  specimens  of  the  spicules. 

LIVING  AND  SECTIONED  MATERIAL. 

1.  Place  a  living  sponge  in  a  watch-glass  of  sea-water,  add  a 
little  powdered  carmine,  and  examine  it  with  the  low  power  of 
your  microscope  for  currents  of  water.     See  if  particles  are  mov- 
ing in  a  definite  direction  near  the  general  surface  and  near  the 
osculum. 

2.  With  a  moderately  sharp  razor  cut  tangential  sections 
of  the  wall,  as  thin  as  possible,  mount  in  sea-water  under  a  cover, 
and  examine  with  a  low  power.    This  will  show  both  incurrent 
and  radial  canals  in  cross-section.     How  can  you  distinguish 
one  from  the  other?     In  a  favorable  place  look  for  moving 
flagella.    Are  flagella  in  all  of  the  canals?     In  favorable  situa- 
tions it  can  be  easily  seen  that  the  cells  that  have  flagella  possess 
collars  also.     (Collars  may  be  withdrawn  by  cells  so  they  pro- 


20  PORIFERA. 

trude  but  slightly).  You  see  now  what  causes  the  current  of 
water.  Do  you  understand  how  a  sponge  feeds?  The  choano- 
cytes  of  the  sponge  resemble  choanoflagellate  protozoons. 

Make  a  drawing  showing  the  arrangement  of  choanocytes. 

Examine  transverse  sections  of  a  specimen  that  has  been 
decalcified  and  stained. 

1.  The  cloacal  chamber  is  lined  by  a  pavement  of  epithelium. 

2.  The  radial  canals  are  lined  by  more  conspicuous  cells, 
the  gastral  epithelium,  or  choanocytes. 

3.  The  incurrent  canals  and  the  outer  surface  of  the  sponge 
are  covered  with  flattened  cells,  the  dermal  epithelium. 

4.  In  a  part  of  the  section  where  a  considerable  area  of  choan- 
ocytes appear  in  surface  view,  look  for  the  prosopyles,  through 
which  the  water  passes  from  the  incurrent  to  the  radial  canals. 
(They  may  not  be  found.) 

5.  Make  out  any  structures  you  can  in  the  area  lying  between 
the  dermal  and  gastreal  layers.     What  cells  are  found  here  ? 

Make  a  drawing  of  several  adjacent  canals  to  show  the  above 
points  and  indicate  the  course  of  the  water  by  arrows. 

6.  In  the  stained  sections,  look  for  single  ova  and  for  spheres 
containing  many  spermatozoa,  the  sperm-spheres.     Look  also 
for  segmenting  eggs,  which  are  frequently  to  be  found.     The 
ova  are  fertilized  while  still  lying  where  they  have  developed, 
just  within  the  choanocyte  layer.     Remaining  in  place,  they 
undergo  cleavage  and  develop  so  far  as  the  amphiblastula  stage 
(see  figures  in  the  text-books).     They  then  break  through  the 
choanocyte  layer  into  the  radial  canals  and  pass  out  with  the 
current  of  water.     Living  specimens  are  frequently  found  with 
such  embryos  issuing  from  the  oscula  in  the  outgoing  current 
of  water.    The  sperm-spheres,  when  fully  developed,  also  break 
through  the  choanocyte  layer  and,  separating  into  their  com- 
ponent spermatozoa,  pass  out  with  the  outgoing  water. 

Ova  and  sperm  are  formed  by  the  same  individual,  and  the 
animal  is  therefore  hermaphroditic,  but  the  products  ripen  at 
different  periods  and  are  seldom  both  present  in  an  individual 
at  the  same  time. 


GRANTIA.  21 

//  the  time  allows,  draw  ova,  sperm-spheres,  segmenting  eggs, 
and  embryos. 

It  is  desirable  to  examine  specimens  of  Leucosolenia,  a  still 
simpler  sponge,  and  of  some  of  the  more  complicated  forms, 
like  commercial  sponges,  Spongilla,  Cliona,  and  Chalina.  Why 
is  more  than  a  single  osculum  desirable  in  such  forms?  Under- 
stand the  relation  of  the  internal  structure  of  the  complicated 
forms  to  the  more  simple  forms.  What  reason  is  there  for  the 
complication? 


COELENTERATA. 

With  a  single  continuous  coelenteron  or  gastro-vascular  cav- 
ity. With  the  exception  of  the  Ctenophora  all  have  nettle  cells. 
There  are  two  cellular  layers  and  a  mesoglea. 

CLASS  1.  Hydrozoa. 

Coelenteron  simple,  without  septa.     Gonads  usu- 
ally ectodermal.     Fully  formed  medusae  have  a 
velum. 
Order  1.  Leptolinse. 

With  a  fixed  zoophyte  stage. 
Suborder  1.  Anthomedusse. 

Without  hydrothecse  or  gonothecse.    The  medusa 
bears  gonads  on  the  manubrium.     (Hydra,  Pary- 
pha.) 
Suborder  2.  Leptomedusse. 

With  hydrothecse  and  gonothecse.     The  medusa 
bears  gonads  on  the  radial  canal.     (Obelia,  Goni- 
onemus.) 
Order  2.  Trachylinse. 

Without  fixed  zoophyte  stage. 
Suborder  1.  Trachymedusse. 

Tentacles   from   the  margin  of  the  umbrella. 
Gonads  on  the  radial  canals.     (Petasus.) 
Suborder  2.  Narcomedusse. 

Tentacles  from  the  exumbrella.    Gonads  on  the 
manubrium.     (JSginopsis.) 
Order  3.  Hydrocorallina. 

Massive  calcareous  exoskeleton.     (Millepora.) 
Order  4.  Siphonophora. 

Pelagic.  Colonial.   Colony  usually  shows  extreme 
polymorphism  of  its  zooids.     (Physalia.) 
CLASS  2.  Scyphozoa. 

Body-wall  of  polyp  thrown  into  four  ridges 
(tsenioles)  which  project  into  the  ccelenteron. 
Medusa  generally  without  velum  and  with  gas- 
tric tentacles.  Medusoid  form  predominating. 
22 


CCBLENTERATA.  23 

Order  1.  Stauromedusse. 

Conical  or  vase-shaped  umbrella.  No  tentacu- 
locysts.  (Tessera.) 

Order  2.  Peromedusse. 

Conical  umbrella  with  transverse  constriction. 
Four  inter-radial  tentaculocysts.  (Pericolpa.) 

Qrder  3.  Cubomedusse. 

Four-sided  umbrella.  With  per-radial  tentacu- 
locysts. Velum  present.  (Charybdea.) 

Order  4.  Discomedusae. 

Saucer-shaped  umbrella.     Per-radial  and  inter- 
radial  tentaculocysts.     (Aurelia.) 
CLASS  3.  Actinozoa. 

With  a  stomodseum,  and  with  mesenteries  ex- 
tending into  the  coelenteron.    Fixed  forms. 
Subclass  1.  Zoantharia. 

Mesenteries  and  tentacles  usually  very  numerous. 

Order  1.  Actiniaria. 

Usually  single.  No  skeleton.  (Metridium.  Sa- 
gartia.) 

Order  2.  Madreporaria. 

Usually  form  colonies  and  always  have  calcare- 
ous exoskeleton.  (Astrangia,  Orbicella,  Mean- 
drina.) 

Order  3.  Antipatharia. 

Tree-like.    Mesenteries  and  tentacles  compara- 
tively few.     Chitinoid  skeleton.     (Cirripathes.) 
Subclass  2.  Alcyonaria. 

Mesenteries  and  tentacles  eight  in  number.  Ten- 
tacles branched. 

Order  1.  Alcyonacea. 

Skeleton  in  the  form  of  small,  irregular  bodies, 
frequently  calcareous  spicules.  (Alcyonium, 
Tubipora.) 

Order  2.  Gorgonacea. 

Tree-like,  with  calcareous  or  horny  exoskeleton. 
No  syphonoglyphes.  (Gorgonia.) 

Order  3.  Pennatulacea. 

Colony  with  one  end  usually  embedded  in  the 
sea-bottom.     (Pennatula,  Renilla.) 
CLASS  4.  Ctenophora. 

Single.  Pelagic.  Eight  rows  of  meridional 
swimming  plates.  No  nettle  cells. 


24  CCELENTERATA. 

Order  1.  Cydippida. 

Nearly  circular.  Two  tentacles,  each  of  which 
may  be  retracted  into  a  sheath.  (Pleurobra- 
chia,  Mnemiopsis.) 

Order  2.  Lobata. 

Compressed  in  the  vertical  plane.  Two  large 
oral  lobes.  No  tentacle-sheaths.  (Deiopea.) 

OrderS.  Cestida. 

Ribbon-shaped.  Two  tentacles  with  sheaths,  and 
numerous  other  tentacles.  (Cestus.) 

Order  4.  Beroida. 

Laterally  compressed.  Without  tentacles. 
(Berce.) 

Mayer:  Mudusae  of  the  World.     Carnegie  Inst.,  Wash.,  1910. 
Nutting:  The  Hydroids  of  the  Woods  Hole  Region.    Bui.  U.  S.  Fish.  Com., 
19,  1899. 


HYDROZOA. 

HYDRA.    (Fresh-water  Polyp.) 

Hydra,  the  'only  common  fresh-water  ccelenterate,  is  fre- 
quently found  in  jars  of  water  taken  from  quiet  pools  or  sluggish 
streams  that  contain  lily-pads,  decaying  leaves,  and  other  vege- 
table matter.  The  animals  may  frequently  be  found  by  examin- 
ing the  surfaces  of  submerged  leaves,  but  it  is  usually  better 
to  allow  such  material  to  stand  in  glass  jars  for  a  day  or  two, 
as  the  animals  then  tend  to  collect  on  the  lighter  sides  of  the 
vessels.  They  are  easily  kept  in  balanced  aquaria. 

Examine  specimens  in  an  aquarium  and  find  what  you  can 
about  their  mode  of  life.  Do  they  form  colonies? 

Place  a  specimen  in  a  watch-glass  of  water  and  examine  it 
with  a  lens. 

1.  What  is  its  shape  and  color?    Is  it  attached?    If  so,  by 
what  part  of  the  body?    Notice  the  circlet  of  tentacles.    How 
many  are  there?    Compare  notes  with  others  and  see  if  all  have 
the  same  number.     How  are  they  placed? 

2.  Does  the  Hydra  move  its  body  or  tentacles?    Is  it  sensi- 
tive?   How  do  you  know? 


HYDRA.  25 

3.  Examine  with  a  low  power  of  the  microscope  and  review 
the  above  points.     You  may  also  be  able  to  see  the  mouth 
around  which  the  tentacles  are  arranged. 

Make  two  drawings,  one  showing  the  animal  expanded  and 
the  other  contracted. 

Place  your  specimen  on  a  slide  under  a  cover-glass  that  is 
supported  by  the  edge  of  another  cover-glass,  so  it  can  be  exam- 
ined with  a  high  power.  Be  careful  not  to  crush  it.  Notice: 

4.  The   outer   layer,   ectoderm.    What   is   its   color?    Is   it 
continuous  over  the  whole  outer  surface  ?    Does  it  vary  in  thick- 
ness?   Are  the  cells  of  which  it  is  composed  apparently  all  alike? 

5.  The  inner  layer,  endoderm.     What  is  its  color?     If  color 
is  present,  is  it  evenly  diffused  or  is  it  collected  in  special  bodies? 
Are  the  cells  of  which  the  endoderm  is  composed  apparently 
all  alike  ?    Do  they  differ  in  appearances  from  those  of  the  ecto- 
derm other  than  in  color?    If  the  specimen  is  not  deeply  colored, 
look  for  flagella  moving  in  the  internal  cavity. 

6.  Examine   the  ectoderm  of  the   tentacles   carefully   and 
notice  that  each  of  the  large,  rounded,  clear  cells,  the  nematocysts, 
shows  a  rather  indefinite  streak  running  from  its  outer  end, 
back  into  the  interior.     See  if  you  can  find  the  trigger  (cnidocil) 
on  any  of  these  cells. 

Draw  a  portion  of  a  tentacle  showing  the  distribution  of  the 
nematocysts. 

7.  Place  your  specimen  under  the  low  power  of  the  micro- 
scope, carefully  run  in  a  drop  of  saffranin,  and  see  if  any  of  the 
nematocysts  are  discharged  when  the  saffranin  touches  them. 
Examine  with  a  high  power  and  notice  the  appearance  of  the 
thread.     Notice  the  change  in  the  shape  of  the   nematocysts 
that  have  discharged.     See  if  you  can  find  two  kinds. 

Make  an  enlarged  drawing  of  an  exploded  nematocyst. 

8.  Examine  prepared  transverse  sections  of  Hydra.     Notice 
that  the  body  is  composed  of  two  layers  of  cells,  between  which 
is  an  almost  structureless  thin  layer.    Do  the  cells  of  the  two 
layers  differ  in  size,  shape,  and  structure?    Do  you  find  more 


26  CCELENTERATA. 

than  one  kind  of  cell  in  each  or  either  of  these  layers?  Where 
are  they?  What  are  they? 

Make  a  careful  drawing  of  the  section  showing  the  arrangement 
as  you  see  it. 

Examine  longitudinal  sections,  for  differences  in  the  char- 
acter of  the  ectoderm  and  endoderm  in  different  parts  of  the 
body. 

9.  Reproduction.  Examine  living  specimens  in  a  watch- 
glass  of  water  for  bud  formation  and  for  sexual  organs.  Sperm- 
aries  are  just  beneath  the  tentacles;  ovaries,  lower  down; 
buds  may  be  found  at  different  levels.  What  layers  of  cells  is 
involved  in  the  formation  of  each  of  these? 

Eggs  are  not  formed  at  all  seasons  of  the  year  and  vary 
greatly  in  appearance  according  to  their  stage  of  development. 

Make  drawings  of  the  stages  of  reproduction  that  you  find. 

Tannreuther:  The  Development  of  Hydra.     Biol.  Bui.,  14,  1908. 
Whitney:  Artificial  Removal  of  the  Green  Bodies  from  Hydra  viridis. 
Biol.  Bui.,  14,  1908. 

OBELIA. 

These  small,  colonial  animals  are  common  on  submerged  or 
floating  wood,  stones,  and  seaweeds,  where  the  water  is  rather  free 
from  sediments.  With  the  aid  of  a  glass-bottomed  pail  they, 
in  company  with  many  other  forms,  may  usually  be  seen  about 
old  wharfs.1 

Note  the  appearance  of  large  colonies  of  this  form  that  are 
growing  on  stones  or  on  pieces  of  board. 

1.  Notice  the  tree-like  form  of  any  single  stem.    Do  the 
branches  have  a  definite  size  and  arrangement? 

2.  At  the  extremities  of  the  branches  are  the  single  individuals, 
hydranths  or  zooids.    Each  is  similar  to  a  single  Hydra  in  cer- 
tain ways,  but  is  inclosed  in  a  vase-like  formation,  the  hydrotheca. 

3.  The  latter  is  a  continuation  of  a  tough,  membranous 
sheath,  the  perisarc,  which  covers  each  part  of  the  whole 
colony. 

1  Campanularia  differs  principally  in  that  it  does  not  set  its  medusae  free. 


OBELIA.  27 

Do  you  notice  any  modifications  of  the  perisarc  below  the 
hydrotheca?  Do  the  modifications  serve  any  purpose? 

4.  Trace  the  stem  down  to  the  creeping,  stolon-like  portion 
of  the  colony,  the  hydrorhiza. 

Make  a  drawing  of  a  colony. 

5.  The  fleshy  continuation  of  the  zooid  down  into  the  stalk 
is  termed  the  coenosarc.     Is  it  in  close  contact  with  the  perisarc? 

6.  In  an  expanded  hydranth,  note  the  mouth,  the  arrange- 
ment of  the  tentacles,  and  the  number  of  tentacles.    How  is  the 
individual  supported  in  its  cup?    Can  you  trace  the  ccelenteric 
cavities  down  through  the  stalks,  and  prove  them  to  be  continuous 
with  each  other?    Motion  in  the  fluid  contents  of  living  speci- 
mens makes  this  easy  to  observe. 

7.  Examine  a  hydranth  with  a  high  power  and  look  for  the 
cell-layers  characteristic  of  coelenterates.    Determine  how  its 
tentacles  differ  from  the  tentacles  of  Hydra,  and  explode  nemato- 
cysts  as  with  Hydra. 

Make  a  drawing  of  a  hydranth. 

8.  Look  for  certain  extremities  which  show  neither  tentacles 
nor  any  opening  in  the  perisarcal  covering.     Such  a  condition 
signifies  either   an  undeveloped   hydranth  or   a  reproductive 
individual.     If  the  latter,  it  is  considerably  swollen  and  is  termed 
a  gonangium.     The  central  core  or  coenosarc  of  a  gonangium,  the 
blastostyle,  should  be  examined  for  medusce  buds.     This  may  re- 
quire a  high  power. 

Make  a  drawing  of  a  gonangium. 

9.  You  may  find  free  medusae  swimming  in  the  dish  where 
material  is  kept.     If  you  do,  you  should  examine  one,  but  it 
will  not  prove  as  satisfactory  for  study  as  a  larger  form,  like 
Gonionemus,  directions  for  the  study  of  which  are  given  further 
over.     In  comparing  it  with  Gonionemus  notice  the  small  size 
of  the  velum,  and  the  usual  everted  position  of  the  bell,  so  the 
manubrium  appears  like  a  handle. 

It  is  not  uncommon  to  find  planulae  escaping  from  gono- 
thecae  of  Campanularia.  Frequently  the  medusse  that  are 
liberated  have  previously  shed  their  eggs. 


28  CCELENTEEATA. 

10.  Study  the  cellular  structure  of  a  hydranth  and  of  a  gon- 
angium,  as  seen  in  cross  and  longitudinal  sections. 

Make  a  drawing  of  each. 

For  comparison  use  any  thecate  forms,  which  may  be  offered 
as  loose  material  or  as  demonstrations,  such  as  Campanularia, 
Sertularia,  and  Plumularia. 

PARYPHA. 

This  form  is  frequently  abundant  on  the  piles  of  old  wharfs, 
where  the  colored  colonies  form  conspicuous  masses  just  below 
low-water  mark. 

Examine  the  general  form  of  a  colony  and  note,  either  with 
a  hand  lens  or  with  the  naked  eye,  the  stem,  or  hydrocaulus,  as 
it  arises  from  the  branching,  matted  hydrorhizal  portion  of  the 
colony.  The  parts  of  the  colony  will  be  seen  to  differ  from  the 
Leptomedusan  (Campanularian)  form  studied,  especially  in 
branching,  rigidity,  hydrothecse,  and  gonangia. 

Make  a  drawing  to  show  the  formation  of  the  colony. 

1.  How  does  a  hydranth  differ  from  the  hydranth  of  Obelia 
in  the  matter  of  tentacles  ?    Is  a  hydrotheca  present  ? 

2.  The  mouth  is  terminal  and  is  situated  at  the  end  of  a 
manubrium. 

3.  The  short  but  rather  large  body  of  the  hydranth  passes 
back  to  the  perisarc  as  the  fleshy  axis,  ccenosarc. 

4.  Notice  the  medusa  buds  on  the  manubrium  between  the 
rows  of  tentacles.    What  is  their  arrangement?    This  is  a  form 
in  which  the  medusae  are  not  set  free,  but  remain  vestigial. 
The  gonads  ripen  on  the   partially  developed   manubrium  of 
the  medusa.    The  sexes  are  separate. 

Make  a  drawing  of  a  hydranth. 

5.  The  arrangement  of  the  attached  medusae  is  best  seen  in 
sections.     In  the  male  medusae  numerous  spermatozoa  will  be 
found,  while  the  female  individuals  have  a  much  smaller  number 
of  large  ova,  which  are  likely  to  be  in  advanced  stages  of  seg- 
mentation. 

The  sections  show  the  same  body  layers  as  Hydra,  and  the 


GONIONEMUS.  29 

derivation  of  the  medusa  as  an  outpocketing  of  the  wall  of  the 
hydranth  is  evident. 

Make  drawings  of  sections  of  male  and  female  reproductive 
organs  (medusa  buds). 

For  comparison,  study  Pennaria,  Margelis,  Hydractinia, 
Clava,  and  Eudendrium. 

Hargitt:  The  Early  Development  of  Penneria  tiarella.     Arch  f.  Entwick- 

lungsmech.^  18,  1904. 

Pearse:  Reactions  of  Tubularia  crocea.     Am.  Nat.,  40,  1906. 
Torrey:  Biological  Studies  on  Corymorpha.    I.  Jour.  Exp.  Zool.,  1,  1904; 

II.  Univ.  Calif.  Pub.  Zool.,  3,  1907. 

GONIONEMUS. 

As  has  been  seen,  the  medusae  buds  are  usually  produced  from 
the  walls  of  a  specialized  hydranth  (Leptomedusae)  or  from  the 
manubrium  wall  of  an  ordinary  hydranth  (Anthomedusae).  A 
series  of  these  buds  in  various  stages  would  show  the  formation 
of  the  umbrella-shaped  individual  with  the  growth  of  the  marginal 
tentacles  around  the  edge.  The  life-history  of  this  form  is  not 
known,  but  from  its  structure  we  are  led  to  believe  that  it 
belongs  to  the  suborder  Leptomedusse.  It  is  found  in  con- 
siderable numbers  throughout  the  summer  in  the  border  of  eel- 
grass  in  the  Eel  Pond  at  Woods  Hole,  where  it  may  be  obtained 
with  a  dip-net.  It  is  more  satisfactory  to  study  than  the  medusa 
of  Obelia,  as  it  is  much  larger  and  its  movements  and  organs 
are  more  easily  observed.  In  plan  of  structure  the  two  are 
quite  similar. 

Put  a  living  specimen  in  a  flat-sided  jar  containing  sea-water, 
or  in  a  finger-bowl,  with  a  black  tile  beneath,  and  notice: 

1.  Its  method  of  locomotion.     To  the  contraction  of  what 
part  of  the  bell  is  movement  due  ?    How  large  is  the  jet  of  water 
that  is  delivered  from  the  bell  ?     Why  is  the  jet  made  narrow  ? 
Does  the  jet  necessarily  leave  at  the  center  or  may  it  be  thrown 
from  one  side  ?    Should  it  be  thrown  from  one  side,  what  would 
be  the  result  ? 

2.  Its  position  in  the  water  when  quiet.    Why  is  this  position 


30  CCELENTEBATA. 

more  desirable  than  the  opposite?    With  a  needle-point  prove 
that  various  parts  of  the  body  are  sensitive. 

With  either  fresh  or  preserved  material  notice: 

1.  Its  flattened  dome-shape.     The  convex  face  is  called  the 
ex-umbrella   (aboral),  while  the  concave  portion  is  termed  the 
sub-umbrella  (oral). 

2.  The  velum  is  the  perforated  diaphragm  that  partly  closes 
in   the   sub-umbrella.    All   medusae   possessing   this   structure 
are  classed  as  Craspedota.    Do  you  understand  its  use? 

3.  In  the  center  of  the  sub-umbrella  is  seen  the  large  pen- 
dent manubrium,  at  the  extremity  of  which  is  a  wide-lipped 
mouth.     If  the  medusa  is  alive,  feed  it  with  small  bits  of  clam 
meat. 

4.  From  the  capacious  sac  at  the  base  of  the  cavity  of  the 
manubrium,  the  stomach,  the  four  radiating  chymiferous  tubes, 
or  canals,  lead  to  the  periphery  of  the  disk,  where  they  open 
into  the  very  delicate  circular  circumferential  canal.    The  four 
radii  marked  out  by  these  canals  are  called  the  per-radii.    Do 
you  understand  the  use  of  these  canals  ? 

5.  The  gonads  hang  from  beneath  the  chymiferous  tubes  into 
the  sub-umbrellar  space.    They  are  lobulated  in  structure,  and 
more  or  less  prominent  according  to  maturity  and  the  breeding 
season.    The  eggs  or  spermatozoa,  as  the  case  may  be,  are  de- 
hisced from  these  into  the  water  directly. 

6.  The  tentacles.    Is  their  arrangement  a  radially  symmetrical 
one?    How  are  the  nematocysts  arranged  on  them?    Look  for 
adhesive  organs  on  them.     Of  what  use  are  such  organs? 

Turn  your  specimen  with  the  velum  side  toward  you  and 
study  the  edge  of  the  medusa  with  a  low-power  objective  for 
the  sense  organs.  These  are  of  two  kinds: 

(a)  The  larger,  round  bodies  at  the  bases  of  the  tentacles 
communicate  with  the  circumferential  canal  (which  may  possibly 
be  seen  along  the  edge  of  the  bell).  They  are  filled  with  a  layer 
of  strongly  pigmented  endoderm  cells  and  are  probably  light- 
percipient  organs. 


HYDROCORALLINA.      SIPHONOPHOKA.  31 

(6)  Other  small  sessile  and  transparent  outgrowths,  situated 
between  the  bases  of  the  tentacles,  are  the  so-called  otocysts, 
which  are  probably  static  organs. 

All  of  the  tentacles  are  abundantly  supplied  with  tactile, 
sensory  cells.  There  is  a  well-established  circumvelar  nerve 
ring  (not  easily  determined  in  living  material)  derived  from  the 
ectoderm,  also  scattering  nerve  cells  beneath  the  ectoderm  in 
connection  with  the  muscular  tissue.  Ex-umbrellar  and  sub- 
umbrellar  layers  of  muscle  fibers  are  also  present. 

Make  a  drawing  from  the  side,  slightly  tipped,  to  show  the  velum, 
and  another  as  seen  from  the  oral  surface. 

Brooks:  Life  History  of  Hydromedusac.  Mem.  Bost.  Soc.  Nat.  Hist.,  3, 
1886. 

Murbach:  The  Static  Function  in  Gonionemus.  Am.  Jour.  Physiol..  10, 
1903. 

Perkins:  The  Development  of  Gonionema  murbachii.  Proc.  Acad.  Nat. 
Sci.,  Phila.,  1902. 

Yerkes:  A  Study  of  the  Reaction  Time  of  the  Medusa  Gonionema  murba- 
chii to  Photic  Stimuli.  Am.  Jour.  Physiol.,  9,  1903. 

HYDROCORALLINA. 

To  this  group  belong  forms  that  have  heavy  calcareous 
exoskeletons.  While  material  is  generally  not  at  hand  to  study 
the  polyps,  it  is  desirable  to  study  and  sketch  the  characteristic 
forms  of  colonies  such  as  Millepora  and  Stylaster,  and  to  note 
the  difference  in  the  distribution  of  pores.  Later  you  will  see 
how  decidedly  these  differ  from  the  ordinary  stony  corals. 

SIPHONOPHORA. 

Examine  living  or  preserved  specimens  of  Physalia,  and 
sketch  the  type  with  reference  to  showing,  if  possible,  the  follow- 
ing structures:  (a)  pneumatophore,  (b)  dactylozooids,  (c)  gastro- 
zooids,  (d)  gonodendrons,  (e)  tentacles.  It  will  be  well  to  refer 
to  a  text-book  to  find  the  positions  and  functions  of  each  of 
.these. 

Bigelow:  The  Siphonophorse.    Mem.  Mus.  Comp.  Zool.,  Harvard,  38, 1911. 


32  CCELENTERATA. 

SCYPHOZOA. 

AURELIA. 

This  form  is  one  of  the  common  jelly-fishes,  and  is  found 
floating  freely  in  the  water.  It  is  frequently  washed  up  on  shore. 
To  be  appreciated  these  medusae  should  be  seen  as  they  occur 
at  the  surface  of  the  sea,  before  they  have  been  handled  or  in- 
jured. Frequently  vast  numbers  may  be  seen  together,  all 
gently  pulsating  and  thus  keeping  near  the  surface.  The  move- 
ment is  very  different  from  that  of  most  hydrozoan  medusae, 
being  very  deliberate  and  graceful. 

If  living  material  is  offered,  study  the  method  of  locomotion 
and  compare  it  with  the  locomotion  of  Gonionemus.  Like  the 
latter,  the  discoid  animal  presents  ex-umbrellar  (aboral)  and  sub- 
umbrellar  (oral)  surfaces,  but  the  edges  of  the  disk  are  indented, 
fringed  with  very  numerous  short  tentacles,  and  a  velum  is 
wanting.  What  difference  does  the  velum  make  in  locomotion? 

The  ex-umbrellar  surface  presents  little  of  interest.  In  the 
live  specimens,  however,  prove  that  the  animal  is  sensitive  over 
this  area  as  elsewhere. 

Preserved  and  hardened  material  is  better  than  living  for  the 
study  of  the  rest  of  the  anatomy  of  this  form.  With  a  specimen 
in  water  in  a  finger-bowl,  with  a  black  tile  for  the  background, 
find  the  following  from  the  sub-umbrellar  surface: 

1.  The  shape  of  the  animal.     Is  the  margin  perfectly  circular 
or  regularly  indented?    Are  all  of  the  marginal  portions  similar? 

2.  Four  large,  fringed  oral  arms  or  lips  hang  from  the  corners 
of  the  nearly  square  mouth,  which  is  located  in  the  center.    No- 
tice how  each  arm  is  similar  to  a  long,  narrow  leaf,  with  the 
sides  folded  especially  along  their  margins.     Examine  the  arms 
for  nematocysts.    Do  you  understand  how  the  animal  gets  its 
food?    If  the  arm  edges  appear  to  be  covered  with  dark  specks 
and  granules,  examine  to  see  if  embryos  may  not  be  entangled. 

3.  The  mouth  is  found  to  lead  by  a  short  gullet  into  a  rather 
spacious  stomach,  which  is  produced  in  the  region  between  each 
two  corners  of  the  mouth  to  form  a  gastric  pouch.    Determine 
the  shape  of  the  stomach. 


AUKELIA.  33 

4.  The  remaining  parts  of  the  digestive  (and  also  in  this 
case  circulatory)   system  include  the  numerous  radial  canals 
and  the  single  circumferential  canal. 

(a)  Directly  beneath  each  oral  arm  a  per-radial  canal  is  given 
off,  which,  at  a  short  distance  from  the  stomach,  gives  off  a 
branch  on  either  side.  The  per-radial  canal  proper  usually 
continues  straight  to  the  marginal  circumferential  canal,  without 
further  subdivision,  but  the  two  side  branches  above  mentioned 
in  turn  subdivide  several  times. 

(6)  From  the  peripheral  wall  of  each  gastric  pouch  three 
canals  pass  toward  the  margin;  the  middle  one  (inter-radial 
canal)  branches  somewhat  after  the  manner  of  the  per-radial 
canals,  but  the  other  two  (ad-radial  canals)  continue  to  the 
circular  canal  without  further  branching.1 

5.  The  position  of  the  gastric  pouches  is  made  clearly  mani- 
fest by  the  gonads,  which  lie  on  the  floor  of  the  pouches,  as  frill- 
like  structures,  horseshoe-shaped,  with  their  open  sides  toward 
the  mouth.    The  ova  or  spermatozoa  are  shed  into  the  stomach  and 
pass  out  of  the  mouth.     Embryos  in  various  stages  of  develop- 
ment may  frequently  be  found  adhering  to  the  oral  arms.    The 
sexes  are  separate.     On  the   sub-umbrellar  surface,   opposite 
each  gonad,  is  a  little  pocket,  the  sub-genital  pit,  which  opens 
freely  to  the  outside.     Whatever  purpose  this  may  serve,  it 
does  not  function  to  conduct  the  genital  products  to  the  outside. 

6.  Parallel  with  the  inner  or  concave  border  of  each  gonad 
is  a  row  of  delicate  gastric  filaments.    These  are  supplied  with 
stinging  cells,  and  they  may  aid  in  killing  live  food  taken  into 
the  stomach.    These  structures  are  not  present  in  the  Hydro- 
zoan  medusa. 

7.  At  the  marginal  extremity  of  each  per-radial  and  inter- 
radial  canal  there  is  an  incision  on  the  edge  of  the  animal,  in 
which  there  are  sensory  organs.     In  each  incision  find : 

(a)  A  tentaculocyst  in  the  form  of  a  short,  club-like  struc- 
ture containing  a  prolongation  of  the  circular  canal.  At  its 

1  In  most  cases  the  foregoing  canals  are  very  evident,  but  if  they  are 
not,  they  may  be  injected  with  water  in  which  carmine  is  mixed,  by  insert- 
ing a  large-mouthed  pipet  into  the  stomach. 
3 


34  CCELENTERATA. 

outer  extremity  are  calcareous  concretions  or  lithites,  and  a  pig- 
ment-spot or  ocellus.  Each  tentaculocyst  is  protected  aborally 
by  a  hood-like  projection,  and  on  the  sides  by  marginal  lappets. 

(6)  Two  depressions,  one  above  and  the  other  below  the 
tentaculocyst.  These  have  been  assigned  olfactory  functions, 
and  are  called  the  olfactory  pits. 

Make  a  drawing  showing  the  profile  of  the  entire  animal,  and 
show  the  structure  of  at  least  one  quadrant,  as  seen  from  the  oral 
surface. 

If  time  permits  study  a  developmental  stage,  "ephyra,"  and 
compare  it  with  the  adult. 

By  way  of  comparison,  examine  demonstrations  of  Cyanea, 
Dactylometraf  Lucernaria,  or  other  forms  belonging  to  this  group. 

Hargitt:  Variations  among  Scyphomedusse.     Jour.  Exp.  Zool.,  11,  1905. 

Hargitt,  C.  W.  and  G.  T. :  Studies  in  the  Development  of  Scyphomedusae. 
Jour.  Morph.,  21,  1910. 

Mayer:  Rhythmical  Pulsation  in  Scyphomedusae.  Carnegie  Inst.  of  Wash- 
ington, 1906. 


ACTINOZOA: 

MBTRIDIUM.    (Sea-Anemone.) 

Specimens  are  quite  common  on  piles,  as  well  as  on  rocky 
bottoms,  and  may  be  easily  observed  by  means  of  a  glass- 
bottomed  pail.  Most  of  the  observations  can  be  made  much 
better  on  specimens  in  aquaria,  but  it  is  desirable  to  see  their 
natural  surroundings. 

1.  Notice  the  shape  and  attachment  of  expanded,  living  speci- 
mens in  an  aquarium,  or  in  a  deep  finger-bowl.     The  free  end, 
called  the  disk  or  peristome,  is  fringed  with  tentacles,  and  the 
elongated  mouth  is  located  in  the  middle  of  this  area.    At  one 
or  both  angles  of  the  mouth  the  lips  are  thickened  into  what  is 
called  a  siphonoglyph. 

Make  a  drawing  of  the  animal. 

2.  Feed  a  specimen  with  bits  of  mashed  clam  to  ascertain 
its  manner  of  taking  in  food.     Drop  bits  on  the  tentacles  at  one 
time,  and  disk  at  another. 


METRIDIUM.  35 

Endeavor  also  to  determine  whether  there  are  currents 
constantly  passing  in  or  out  of  the  mouth  that  are  due  to  ciliary 
action. 

3.  Irritate  the  animal  and  observe  its  manner  of  contraction. 
When  fully  contracted,  if  the  irritation  is  continued,  thread- 
like structures,  acontia,  are  thrust  out  through  minute  pores, 
cinclides,  in  the  body-wall. 

Make  a  drawing  of  the  contracted  animal. 

Internal  Anatomy.— Using  preserved  material,  place  the  edge 
of  a  razor  across  the  peristomial  area,  at  right  angles  to  the 
mouth-slit,  and  divide  the  animal  from  disk  to  base  into  halves. 

1.  Note  the  extent  of  the  esophagus  and  siphonoglyphes; 
they  lead  into  the  coelenteric  chamber.     Find  the  extent  of  this 
chamber,  and  the  method  of  its  subdivision  by  delicate  parti- 
tions, the  mesenteries,  or  septa.    Are  all  of  the  mesenteries  alike  ? 

2.  Forming  the   free  edges  of  the   mesenteries,   below  the 
esophagus,  are  the  convoluted  mesenteric  filaments,  which  are 
secretory  organs  that  are  probably  equivalent  to  the  gastric 
filaments  of  the  Scyphozoa. 

3.  Quite  near  the  bases  of  the  mesenteries  are  the  attachments 
of  the  acontia.     What  relation  have  they  to  the  mesenteric  fila- 
ments? 

4.  Also  located  on  the  mesenteries,  and  arranged  parallel 
to  the  filaments,  but  back  from  the  edge  a  bit,  are  the  repro- 
ductive organs  or  gonads.     Are  they  found  on  all  of  the  mesen- 
teries?   The  ova  or  spermatozoa  are  shed  into  the  coelenteric 
chamber  and  pass  out  through  the  mouth. 

Cut  one  of  the  halves  of  your  specimen  transversely  in  the 
region  of  the  esophagus,  and  study  the  arrangements  of  the 
mesenteries,  their  attachments,  etc. 

5.  How  many  pairs  of  primary  mesenteries,  i.  e.,  those  attached 
both  to  the  outer  body-wall  and  to  the  esophagus,  are  there? 
The  directive  septa  are  those  at  the  angles  of  the  esophageal  tube. 
The  portion  of  the  coelenteric  cavity  between  any  two  pairs 
of  mesenteries  is  termed  an  inter-radial  chamber.     The  space 
between  the  two  mesenteries  of  each  pair  is  called  an  intra- 
radial  chamber. 


36  CCELENTERATA. 

6.  Carefully  determine  the  disposition  of  the  longitudinal 
retractor  muscles  on  the  mesenteries.     Do  they  occupy  similar 
positions  on  all  of  the  mesenteries  ? 

7.  Examine  the  upper  parts  of  the  mesenteries  for  openings, 
septal  stomata,  that  put  the  chambers  in  communication 

8.  Are  the  tentacles  solid  or  hollow? 

Make  a  drawing  of  a  longitudinal  section  and  another  of  a 
cross-section.  Put  into  these  all  of  the  points  of  the  anatomy  you 
have  seen. 

If  time  and  opportunity  permit,  it  is  very  desirable  that  this 
form  should  be  compared  with  specimens  of  the  order  Madre- 
poraria,  and  later  with  the  Alcyonaria.  Such  a  form  as  Astran- 
gia  may  easily  be  obtained  either  alive  or  properly  preserved, 
and  will  serve  to  show  the  relation  of  the  hard  parts  of  the  coral 
to  the  polyp.  You  should  understand  the  relation  of  the  septa 
and  the  mesenteries,  and  of  the  polyps  to  each  other.  If  speci- 
mens are  at  hand,  compare  such  forms  as  Orbicella,  Favia,  and 
Meandrina,  or  any  forms  that  show  gradations  from  separate 
calices  to  fused  groups,  and  understand  the  positions  of  mouths, 
the  arrangement  of  the  ccelenteric  chambers,  and  the  way  in 
which  the  colony  has  come  to  its  present  form.  You  should 
also  examine  large  branching  colonies  and  determine  why  branches 
are  formed  and  how  they  arise. 

Examine  the  structure  of  an  Alcyonarian  colony  and  see 
how  the  polyps  are  placed.  The  structure  of  the  expanded 
polyps  is  nicely  shown  by  Renilla.  The  spicules  of  such  forms 
as  Gorgonia  may  be  obtained  by  boiling  a  portion  of  a  colony 
in  caustic  potash.  What  purpose  do  such  spicules  serve? 

Parker:  The  Reactions  of  Metridium  to  Food  and  Other  Substances. 
Bui.  Mus.  Comp.  Zool.  Harvard,  29,  1896. 

:  The  Mesenteries  and  Siphonoglyphes  in  Metridium  marginatum. 

Bui.  Mus.  Comp.  Zool.,  Harvard,  30,  1897. 

:  Longitudinal  Fission  in  Metridium  marginatum.  Bui.  Mus.  Comp. 

Zool.,  Harvard,  35,  1899. 

:  The  Reversal  of  the  Effective  Stroke  of  the  Labial  Cilia  of  Sea- 
Anemones  by  Organic  Substances.  Am.  Jour.  Physiol.,  14,  1905. 


MNEMIOPSIS.  37 


CTENOPHORA. 

MNEMIOPSIS. 

This  form  belongs  to  the  group  of  'animals  popularly  called 
"comb-jellies,"  and  occurs  along  the  coast  in  irregular  abun- 
dance during  the  summer  months.  Specimens  are  very  phos- 
phorescent when  disturbed,  so,  when  they  are  abundant,  the 
display  caused  by  them  while  rowing  at  night  is  sometimes  bril- 
liant. They  may  frequently  be  seen  during  the  daytime  and  can 
often  be  satisfactorily  observed  in  the  shade  of  a  wharf  when  the 
water  is  calm. 

Unmutilated,  living  material  can  be  studied  to  best  advan- 
tage, but  preserved  material  may  be  had  that  is  quite  satisfac- 
tory for  anatomic  study. 

1.  In  general  appearance  a  specimen  resembles  a  hydrozoan 
medusa,  with  its  aboral  surface  elongated  until,  as  a  whole,  it 
approaches  the  shape  of  a  fowl's  egg. 

2.  The  broader  or  oral  end  bears  two  heavy  terminal  lobes, 
between  the  bases  of  which  is  the  slit-like  mouth.    We  may  con- 
sider the  elongation  of  the  mouth  to  be  in  the  antero-posterior 
line.     A  bilateral  symmetry  is  thus  evident. 

3.  On  each  lateral  surface  of  the  animal,  midway  between 
the  terminal  lobes,  at  a  short  distance  from  the  mouth,  notice  a 
small  opaque  spot,  an  undeveloped  tentacle  in  its  sheath. 

4.  At  the  aboral  pole  is  a  depression,  in  the  bottom  of  which 
is  the  "sensory  body." 

5.  Leading  away  from  this  and  extending  as  meridional 
lines  toward  the  oral  pole,  are  eight  ctenophoral  rows,  or  swim- 
ming plates.     Examine  the  plates  with  a  hand-lens  and  deter- 
mine their  structure  and  function.    A  pair  of  rows   (arising 
from  the  pit  of  the  sensory  body  as  a  single  row)  extends  down 
over  each  terminal  lobe.    Another  pair  passes  down  each  lateral 
surface  of  the  animal.    Each  of  these  lateral  rows,  after  passing 
half-way  to  the  mouth,  changes  its  appearance  somewhat,  and 
leaves  the  surface  of  the  body  proper,  being  continued  down  one 
edge  and  up  the  other  of  a  finger-like  process  which  hangs  orally, 


38  CCELENTERATA. 

called  an  auricle.  Each  ctenophore  then  possesses  four  auricles, 
which  are  somewhat  covered  over  by  the  loose  edges  of  the 
terminal  lobes.  The  fringe  of  cilia  which  borders  each  auricle 
is  continuous  with  a  fringe  which  extends  up  and  down  the 
inner,  lateral  edge  of  each  terminal  lobe.  Do  you  understand 
how  the  animal  gets  its  food? 

Digestive  System. — With  a  pipet  inject  a  solution  of  carmine 
into  the  mouth  opening. 

1.  You  can  then  more  plainly  see  the  long  ribbon-like  esoph- 
agus, which  leads   to  a  very  small   stomach  just   beneath  the 
sensory  body. 

2.  From  the  stomach  are  given  off  the  canals,  which  in  a 
successful  injection  will  be  seen  to  be  as  follows : 

(a)  Two  short  "excretory  canals"  opening  into  the  pit  where 
the  sensory  body  is  located. 

(6)  Two  esophageal  canals,  one  on  each  side,  passing  down 
along  the  esophagus. 

(c)  Two  tentacular  canals,  one  on  each  side,  passing  to  the 
tentacular  structure  of  that  side. 

(d)  Four  meridional  canals,  each  of  which  bifurcates.     The 
eight  thus  formed  pass  down  the  animal  superficially,  just  beneath 
the  ctenophoral  rows. 

Reproductive  System. — The  ctenophore  is  hermaphroditic 
and  ova  and  spermatozoa  are  proliferated  from  the  walls  of  the 
meridional  vessels. 

A  portion  of  a  ctenophoral  row  should  be  cut  off,  and  exam- 
ined under  a  microscope,  to  ascertain  the  arrangement  and  rela- 
tion of  plates  and  cilia. 

Make  a  drawing  of  a  side  view. 

Make  a  diagram  that  will  show  the  appearance  of  a  merid- 
ional cross-section. 

Abbott:  The  Morphology  of  Coeloplana.     Zool.  Jahrb.,  24,  1907. 

A.  Agassiz :  Embryology  of  the  Ctenophorse.     Am.  Acad.  Arts  and  Sci.,  10, 

1874. 
Mayer:  Ctenophores  of  the  Atlantic  Coast  of  North  America.     Carnegie 

Inst.  of  Washington,  1912. 
Parker:  The  Movements  of  the  Swimming-Plates  in  Ctenephores,  with 

Reference  to  the  Theories  of  Ciliary  Metachronism.    Jour.  Exp.  Zool.,  2, 

1905. 


PLATYHELMNTHES. 

Body  elongated,  flattened  and  unsegmented.    Anus  gener- 
ally absent. 

CLASS  1.  Turbellaria. 

Outer  surface  ciliated.     Free  living. 

Order  1.  Polycladida. 

Intestine  complexly  branched.  No  separate 
vitellaria.  (Planocera,  Leptoplana,  Stylochus.) 

Order  2.  Tricladida. 

Intestine  with  anterior  median,  and  two  posterior 
lateral  limbs.  Vitellaria  numerous.  (Planaria, 
Bdelloura,  Synccelidium.) 

Order  3.  Rhabdoccelida. 

Simple,  sac-like  intestine.     Body  usually  elon- 
gated.    (Polychcerus,  Microstomum.) 
CLASS  2.  Trematoda. 

Parasitic.  Generally  with  sucking  disks.  Well- 
developed  digestive  system. 

Order  1.  Monogenetica. 

Ectoparasitic.  Direct  development.  Three  or 
more  suckers.  (Polystomum.) 

Order  2.  Digenetica. 

Endoparasitic.  Complicated  development.  Never 
more  than  two  suckers.     (Distomum.) 
CLASS  3.  Cestoda. 

Endoparasitic.  Without  digestive  cavity.  Usu- 
ally having  a  scolex,  bearing  clinging  organs 
(suckers  or  hooks). 

Order  1.  Monozoa. 

Body  not  divided  into  proglottids.  (Caryophyl- 
Iseus.) 

Order  2.  Polyzoa. 

Body  consisting  of  scolex  and  proglottids.     (Tae- 
nia,  Crossobothrium.) 
39 


40  PLATYHELMINTHES. 

CLASS  4.  Nemertinea. 

Elongated,  ciliated,  with  eversible  proboscis  not 
directly  connected  with  the  alimentary  canal. 
Intestine  usually  with  lateral  diverticula.  Anus 
present.  (Tetrastemma,  Cerebratulus.) 


TURBELLARIA. 

PLANARIA  MACULATA. 

This  form  is  very  common  in  fresh-water  ponds  throughout 
the  United  States.  It  is  found  during  the  day  on  the  lower  or 
shaded  surfaces  of  stones  and  other  submerged  objects,  a  fact 
which  suggests  that  it  is  nocturnal  in  its  habits.  Most  fresh- 
water planarians  have  very  opaque  bodies  and  their  internal 
organization  cannot  be  studied  in  the  fresh  specimens. 

1.  Notice  the  general  shape  of  the  body. 

2.  The  methods  of  locomotion.     Look  for  cilia. 

3.  The  pharynx  and  mouth  near  the  middle  of  the  ventral 
surface. 

4.  The  eye-spots  on  the  anterior  dorsal  surface. 

5.  Try  feeding  specimens  by  crushing  a  live  pond-snail  and 
putting  the  fragments  in  the  dish  with  them.     If  any  of  the 
worms  are  at  rest,  set  them  in  motion  by  lifting  one  end  of  each 
with  a  bit  of  wood  or  some  blunt  instrument.     Observe  the  ani- 
mals at  intervals  of  a  few  minutes  and  see  if  any  of  them  begin 
to  feed.     If  so,  by  turning  them  over  quickly  with  a  blunt  instru- 
ment, try  to  see  how  the  pharynx  is  used.     If  not  successful, 
try  turning  a  specimen  ventral  side  up,  and  placing  a  small  bit 
of  snail  meat  on  its  body  in  the  region  of  the  pharynx. 

6.  Look  among  the  specimens  in  the  dishes  on  the  prepara- 
tion table  for  animals  that  show  marks  of  normal  fission. 

7.  Clean  a  heavy  watch-glass  thoroughly  and  pour  it  about 
two-thirds  full  of  clean  pond-water  from  the  jar  on  the  prepa- 
ration table.     Transfer  all  of  the  specimens  to  this  dish,  lifting 
each  carefully  with  a  bit  of  wood.     With  a  scalpel  mutilate  them 
in  various  ways;   cut  one  in  two  transversely,  another  longitu- 
dinally, another  into  several  pieces  of  various  shapes.    Make 


BDELLOURA  OR  SYNCCELIDIUM.  41 

memoranda,  if  necessary,  of  the  shapes  of  the  various  pieces. 
Carefully  cover  the  dish  and  set  it  away.  Examine  the  pieces 
with  a  hand-lens  every  twenty-four  hours  for  the  next  week  or 
ten  days.  If  the  water  in  the  dish  begins  to  show  signs  of  becom- 
ing foul,  transfer  the  pieces  to  a  clean  dish  of  fresh  pond-water. 
Do  not  use  water  from  the  tap. 

Curtis:  The  Life  History,  the  Normal  Fission,  and  the  Reproductive  Organs 
of  Planaria  maculata.  Proc.  Bost.  Soc.  Nat.  Hist.,  30,  1902. 

Morgan:  Experimental  Studies  of  the  Regeneration  of  Planaria  maculata. 
Arch.  f.  Entwickelungsmech.,  7,  1898. 

Parker  and  Bennett :  The  Reactions  of  Planarians  with  and  without  Eyes  to 
Light.  Am.  Jour.  Physiol.,  4,  1900. 


BDELLOURA  OR  SYNCOELIDIUM. 

Most  triclads  are  free-living,  but  a  few  are  ectoparasites. 
The  above-mentioned  forms  are  found  upon  the  proximal  joints 
of  the  walking  legs  and  in  the  gill-books  of  Limulus.  Owing  to 
the  absence  of  pigment,  they  are  very  favorable  for  the  study 
of  internal  structure,  and  may  be  used  to  demonstrate  the  struc- 
tures not  observed  in  Planaria  maculata. 

1.  Observe  the  movements  of  the  living  worms  in  a  watch- 
glass  of  sea-water;  then  place  a  specimen  on  a  slide,  dorsal  side 
uppermost,  and  cover  with  a  slip. 

If  any  of  the  points  of  structure  mentioned  for  Planaria  have 
not  been  observed,  try  to  find  them  on  this  form. 

2.  Notice  that  the  gut  with  its  three  main  branches  (triclad 
type)   and  many  secondary  diverticula  is  easily  recognizable. 
The  mouth  can  sometimes  be  made  out  as  a  small  circular  open- 
ing leading  ventrally  from  the  posterior  end  of  the  pharyngeal 
sheath. 

Compress  the  specimen  as  much  as  possible  by  drawing  off 
the  water  with  filter-paper  and  look  for: 

3.  The  cerebral  ganglia,  a  bilobed  structure  beneath  the  eye- 
spots,  that  appears  as  a  slightly  lighter  area. 

4.  From  the  cerebral  ganglia  two  longitudinal  nerve  cords 
pass  backward,  and  several  smaller  nerves  pass  off  in  front.     Ex- 
amine the  specimen  by  reflected  light,  looking  particularly  at 


42  PLATYHELMINTHES. 

the  nervous  system  and  pharynx.  What  relation  have  the  nerve 
cords  behind? 

5.  With  the  high  power  and  good  light,  look  for  the  water- 
vascular  tubules.  The  region  anterior  to  the  cerebral  ganglia 
is  a  favorable  place.  They  form  a  clear,  branching  tracery,  a 
little  lighter  than  the  surrounding  tissue.  The  flicker  of  the 
flame  cells  can  usually  be  seen,  but  they  may  be  more  easily  seen 
in  Crossobothrium.  Examine  chart  and  text-book  figures  of  the 
water-vascular  system. 

Make  a  good-sized  drawing  of  a  worm,  showing  the  above 
points. 

Reproductive  Organs. — Turbellarian  worms  are  hermaphro- 
ditic. In  this  form  the  various  organs  are  so  crowded  together 
that  it  will  be  best  to  follow  each  system  separately.  Com- 
press a  specimen  under  the  slip  and  find  the  male  organs  as  fol- 
lows: 

(a)  The  testes  are  the  numerous  rounded  masses  between 
the  lateral  branches  of  the  gut.  They  are  connected  by  means 
of  fine  tubes  which  cannot  be  seen  in  fresh  specimens. 

(6)  The  vasa  deferentiaf  two  large  tubes,  one  on  either  side 
of  the  pharynx,  that  unite  posteriorly  near  the  base  of  the  penis. 

(c)  The  genital  atrium,  within  which  the  penis  lies  with- 
drawn, is  situated  behind  the  pharynx.  The  penis  and  atrium 
may  be  considered  as  a  replica,  in  miniature,  of  the  pharynx 
and  its  sheath. 

If  the  above  structures  cannot  be  satisfactorily  seen,  try 
preserved,  stained,  and  mounted  specimens.1 

Draw  the  male  reproductive  system.  Refer  to  charts  and 
text-books  for  anything  that  is  obscure. 

1  Specimens  may  be  readily  killed  by  compressing  under  a  slip,  being 
careful  to  draw  the  excess  of  fluid  out  on  one  side  so  that  the  animal 
cannot  contract,  and  running  in  killing  fluid.  (Sublimate  acetic  is  good.) 
As  soon  as  they  become  opaque  white,  put  on  enough  killing  fluid  to  float 
the  slip  off  and  transfer  the  specimens  to  a  dish  of  the  fixative  for  five 
minutes,  then  50  percent  alcohol  a  few  minutes,  70  percent  several  hours, 
stain  with  borax  carmine  or  Delafield's  hematoxylin;  dehydrate,  clear  and 
mount  in  balsam.  (See  directions  in  the  appendix  for  making  permanent 
preparations.) 


BDELLOURA   OR   SYNCCELIDIUM.  43 

The  female  organs  are  as  follows: 

(a)  Opening  into  the  genital  atrium  are  the  two  large  sacs, 
the  so-called  uteri,  which  lie  near  the  margins,  just  posterior  to 
the  end  of  the  pharynx.  Each  has  a  separate  opening  on  the 
ventral  surface  of  the  body,  but  has  no  direct  connection  with 
any  other  part  of  the  reproductive  system.  These  may  not 
be  homologous  with  the  single  uterus  found  in  most  triclads. 
(See  Wheeler.) 

(6)  Place  a  worm  ventral  side  up  and  look  carefuly  be- 
tween the  second  and  third  or  the  third  and  fourth  anterior  gut 
diverticula  on  either  side  of  the  main  anterior  ramus  for  the 
two  ovaries. 

(c)  The  oviducts  pass  backward  from  the  ovaries,  parallel 
to  the  vasa  deferentia,  and  unite  posterior  to  the  penis.    The 
common  duct  thus  formed  enters  the  posterior  part  of  the  geni- 
tal atrium.    The  oviduct  is  difficult  to  demonstrate  and  it  may 
be  necessary  to  try  both  fresh  and  stained  material. 

(d)  Along  the  margins  of  the  animal,  between  the  divertic- 
ula of  the  gut,  are  rounded  bodies,  the  wtellaria.    These  dis- 
charge their  products  into  the  oviducts.    Do  you  know  what 
they  are  for? 

Draw  the  female  reproductive  system. 

Study  stained  and  mounted  specimens  for  any  points 
which  have  not  been  found,  and  particularly  examine  the  ner- 
vous system.  Look  for  the  marginal  nerve  running  along  the 
edge  of  the  body,  and  for  numerous  transverse  commissural 
nerves.  How  many  of  these  are  there?  How  regular  is  their 
arrangement?  * 

Wheeler:  Synccelidium  pellucidum,  a  new  Marine  Triclad.    Jour.  Morph., 
9,  1894. 

1  A  Polyclad,  Planocera,  can  be  obtained  without  difficulty  from  the 
mantle  chamber  of  Sycotypus.  If  Sycotypus  is  allowed  to  remain  out  of 
water  for  some  hours  the  Planocera  usually  crawl  out.  The  form  is  fairly 
satisfactory  for  study. 


44  PLATYHELMINTHES. 

TREMATODA. 

Trematodes  are  flat  worms  which  lead  a  wholly  parasitic 
life,  but  which  have  retained,  to  a  greater  or  less  degree,  those 
organs  that  characterize  free-living  animals.  Some  Trematodes 
are  parasitic  upon  the  outside  (or  ectoderm)  of  other  animals, 
and  are  hence  called  " ectoparasites." 

HABMATOLOECHUS  (DISTOMUM). 

This  form  is  found  as  a  parasite  in  the  lungs  of  frogs.  In 
some  localities  a  large  proportion  of  the  frogs  are  infested  and 
several  specimens  are  frequently  found  in  one  frog.  The  host 
of  the  asexual  generation  of  this  species  is  not  known,  but  in  a 
closely  allied  species  the  asexual  generation  lives  in  the  pond- 
snail.  The  living  worm  is  cylindrical  and  pointed  at  both  an- 
terior and  posterior  ends.  With  a  low-power  objective  note : 

1.  The  anterior  sucker,  surrounding  the  mouth. 

2.  The  ventral  sucker,  near  the  middle. 

3.  Do  you  find  eyes  ? 

4.  The  alimentary  canal. 

(a)  Mouth. 

(b)  The  muscular  pharynx. 

(c)  Soon  after  leaving   the   pharynx   the  intestine  divides 
into  two  equal  branches,  which  pass,  one  on  the  left  and  one  on 
the  right  side,  to  near  the  end  of  the  body.    These  intestinal 
branches  do  not  send  out  lateral  branches  as  they  do  in  Bdel- 
loura. 

The  Water-vascular  System. — A  small  opening  will  be  found 
at  the  posterior  end  of  the  body  from  which  a  duct  passes  forward 
in  a  median  position  to  a  point  a  little  posterior  to  the  median 
sucker.  Here  it  divides  and  sends  a  branch  on  either  side  of 
the  worm  to  near  the  anterior  end. 

The  Nervous  System. — This  is  difficult  to  see,  but  on  either 
side  of  the  pharynx  a  small,  deeply  stained  mass,  the  cerebral 
ganglia,  may  be  visible.  Three  pairs  of  longitudinal  nerves  pass 
back  to  near  the  posterior  end  of  the  body. 


H^MATOLCECHUS    (DISTOMUM).  45 

Make  a  drawing  showing  the  above  structures  as  far  as  you 
have  seen  them. 

The  Reproductive  Organs. — Male:  Two  large  bodies,  the 
testes,  very  definite  in  outline,  occupy  the  posterior  end  of  the 
worm.  A  duct  from  each,  the  vas  deferens,  passes  forward, 
and  the  two  unite  just  posterior  to  the  point  where  the  intestine 
branches.  By  means  of  a  median,  common  duct,  they  open 
to  the  exterior  through  the  male  genital  opening.  This  is  situ- 
ated on  the  ventral  surface,  just  below  the  point  where  the 
intestine  branches. 

Female:  Some  of  the  ducts  are  difficult  to  see,  and  in  many 
cases  they  cannot  be  followed,  but  some  of  the  organs  can  be 
found  in  most  of  the  specimens. 

The  ovary  is  a  lobed  organ  lying  a  little  to  one  side  of  the 
middle  of  the  animal,  and  just  anterior  to  the  testes.  Lying 
against  it  is  the  sac-like  ootype,  into  which  the  ovary  opens. 
From  the  posterior  end  of  the  ootype  the  long,  coiled,  duct- 
like  uterus  passes  backward  to  near  the  posterior  end  of  the  worm, 
turns  and  passes  forward,  and  finally  opens,  at  a  point  on  the 
ventral  surface  near  the  male  opening.  The  uterus  of  an  adult 
worm  usually  contains  embryos  and  fills  the  body,  so  as  to  ob- 
scure the  other  parts. 

The  vitellaria  consist  of  numerous  small,  rounded  masses  that 
lie  near  the  margins  of  the  animal.  The  products  of  these  organs 
are  emptied  into  the  ootype  through  a  short  common  duct,  just 
ventral  to  the  ootype.  Do  you  know  what  they  are  for?  Laurer's 
canal  is  a  short  duct  which  leads  from  the  ootype  to  the  exterior. 
Its  function  is  doubtful. 

Goto:  Studies  on  the  Ectoparasetic  Tremetodes  of  Japan.     Jour.  Col.  Sci. 

Imp.  Univ.  Tokyo,  8,  1894. 
Linton:  The  Process  of  Egg  Making  in  the  Trematode.     Biol.  Bui.,  14, 

1908. 
Leuckart:  Die  Blasenwurmer  und  ihre  Entwicklung.     1856. 

:  Die  Parasiten  des  Menchen. 

Schauinsland :  Beitrag  zur  Kenntnis  der  Embryonalentwicklung  der  Tre- 

metoden.     Jen.  Zeit.  f.  Naturwiss.  Neue  Folge,  9,  1883. 
Thomas :  Development  of  the  Liver  Fluke.    Quart.  Jour.  Mic.  Sci.,  23, 1883. 


46  PLATYHELMINTHES. 

CESTODA. 

The  Cestoda  are  endoparasites  which  possess  very  few  of 
those  organs  that  are  characteristic  of  free-living  animals.  They 
have  no  alimentary  canal,  no  organs  of  special  sense,  and, 
except  in  the  head,  the  nervous  system  is  feebly  developed. 
On  the  other  hand,  the  organs  needed  for  the  reproduction  of 
the  species  are  enormously  developed,  so  that  in  the  more  mature 
portions  of  the  animal,  the  ovaries,  testes,  and  accessory  organs 
occupy  nearly  the  whole  space.  Can  you  explain  why  this  is 
true? 

CROSSOBOTHRIUM  LACINIATUM. 

This  form  passes  its  adult  life  in  the  intestine  (spiral  valve) 
of  the  sand-shark.  Cestode  larvae  which  may  be  the  young  of 
this  species  are  abundant  in  the  cystic  duct  of  the  squeteague. 
How  the  developing  eggs  and  embryos  are  conveyed  from  the 
shark  to  the  squeteague  is  not  known.  The  transfer  of  the 
larvae  from  the  squeteague  to  the  alimentary  canal  of  the  shark 
can  be  easily  understood. 

Adult  Stage. — 1.  Notice  specimens  that  are  attached  to  the 
wall  of  the  intestine  of  the  shark. 

2.  Observe  movements  of  specimens  in  a  dish  of  sea-water. 
Do  the  suckers  have  independent  movements? 

3.  With  a  low  power  of  the  compound  microscope,  or  with 
a  hand-lens,  note  that  the  worm  is  made  up  of  a  head  portion, 
the  scolex,  and  of  numerous  segments,  the  proglottids.    What 
is  the  relative  size  of  the  proglottids  in  the  different  regions  of 
any  specimen?    Where  are  new  proglottids  produced?     (See 
Curtis.)     Are  the  proglottids  attached  to  one  another  with 
equal  firmness  in  all  parts  of  the  body?    Note  their  peculiar 
shape,  and  how  they  are  connected  together.     In  the  above  ex- 
amination, if  living  material  is  used  it  will  often  be  desirable  to 
stretch  portions  of  the  animal  very  gently  with  your  forceps. 

4.  Note  the  number  and  arrangement  of  the  disk-like  suck- 
ers.   How  are  they  borne  on  the  scolex?    Do  you  find  each 
sucker  to  be  entirely  simple  ? 

Draw  the  adult  worm. 


CROSSOBOTHRIUM   LACINIATUM.  47 

5.  Cut  from  the  head-end  of  a  living  specimen  a  piece  con- 
sisting of  a  scolex  and  not  more  than  one  or  two  proglottids. 
Place  this  on  a  slide,  cover,  being  careful  not  to  compress  too 
much  at  first,  and  examine  the  scolex  carefully  again  to  make 
sure  you  understand  its  structure. 

6.  Look  for  transparent  tubes  coiling  about  in  the  scolex 
and  Hs  suckers.     Compress  the  specimen  by  drawing  off  as  much 
water  as  possible  with  filter-paper,  and  look  again  for  the  trans- 
parent tubes.    These  are  portions  of  the  water-vascular  system. 
Recall  the  description  of  this  system  given  in  the  lecture  or  in 
text-books.     The  finer  branches  which  lead  from  the  main  trunks 
are  difficult  to  identify  with  certainty,  but  by  using  the  high  power 
of  your  microscope,  and  focusing  just  below  the  surface  in  the 
more  transparent  portions  of  the  scolex,  the  flame  cells  may  easily 
be  seen.    The  "  flame  "  appears  like  a  short,  thick  whip  lost  in  con- 
tinual vibration.    Find  such  flames  and  watch  them  carefully.    If 
not  found  at  once,  let  the  preparation  stand  and  examine  in  about 
half  an  hour.    In  the  older  preparation  they  are  frequently  easier 
to  find. 

7.  In  both  scolex  and  proglottids  of  fresh  specimens  many 
clear,  transparent,  thread-like  muscle  fibers  may  be  seen.    There 
will  also  be  found  an  abundance  of  clear,  rounded  granules  of 
lime. 

8.  Watch  the  movements  of  the  large,  detached  proglottids. 
Pull  proglottids  from  the  posterior  end  of  the  specimen  to  see  how 
easily  they  may  be  detached.     Very  many  tape-worms  have  these 
"  motile  proglottids,"  which  in  some  cases  remain  alive  for  so  long 
after  being  detached  as  to  seem  almost  like  independent  animals. 

Mount  stained  specimens  of  proglottids  in  balsam  and  study 
the  reproductive  organs.1 

1.  On  one  side  of  the  proglottid  the  lateral  genital  aperture 
will  be  seen.  The  penis  is  a  long,  slender  organ,  found  pro- 
truding, or  lying  in  its  sheath  near  the  lateral  aperture.  The 
vas  deferens,  a  long,  convoluted  tube,  extends  from  the  penis 

1  Specimens  may  be  killed  in  the  manner  described  for  Bdelloura. 
Enough  pressure  should  be  used  to  flatten  the  proglottids  decidedly. 


48  PLATYHELMINTHES. 

to  the  testes,  which  form  many  rounded,  deeply  stained  struc- 
tures that  lie  about  the  oval  outline  of  the  uterus.  On  leaving 
the  penis  the  vas  deferens  extends  toward  the  pointed  end  of 
the  proglottid,  along  the  side  of  the  uterus,  until  it  reaches  a 
point  anterior  to  it,  where  it  may  sometimes  be  seen  sending 
branches  to  the  testes,  but  is  frequently  lost.  Throughout  its 
length  it  is  greatly  convoluted  and  is  generally  filled  with  sper- 
matozoa. 

2.  At  the  base  of  the  penis,  in  the  lateral  genital  aperture, 
is  the  external  opening  of  the  female  organs'.     From  this  point 
a  small  tube,  the  vagina,  leads  to  a  point  below  the  sac-like 
uterus,  which  is  sometimes  very  large  and  sometimes  collapsed 
and  small.     The  vagina  ends  in  a  small  pouch,  the  ootype,  from 
which  a  short  canal  (sometimes  visible,  but  more  often  obscured 
by  the  vagina,  which  lies  above  or  below  it)  leads  to  the  uterus. 

3.  The  ovary  consists  of  a  large  many-fingered  mass  in  a 
median  position,  near  the  posterior  end  of  the  proglottid.     It 
surrounds,  more  or  less  completely,  the  end  of  the  vagina  and 
ootype. 

4.  The  vitelline  glands  occupy  the  posterior  corners  of  the 
proglottid  and  may  extend  anteriorly  along  its  margins,  by  the 
sides  of  the  testes,  nearly  to  its  anterior  extremity.    The  ducts 
from  the  vitelline  glands  unite  and  join  the  ootype. 

5.  The  shell  gland  is  a  small  median  mass  that  is  situated 
between  the  lobes  of  the  ovary  around  the  ootype. 

From  the  lecture  and  figures,  understand  the  relation  of  the 
ducts  of  these  glands  and  the  vagina  to  the  ootype  and  uterus, 
how  and  where  the  eggs  are  fertilized,  and  how  they  are  finally 
lodged  in  the  uterus.  Why  should  hermaphroditism  occur  in 
this  form? 

Draw  a  figure  of  the  proglottid  showing  all  of  the  parts  you 
have  seen. 

Larval  Stage. — Examine  and  draw  a  specimen  of  the  larva 
found  in  the  cystic  duct  of  the  squeteague.  The  scolex  with 
its  suckers  at  the  anterior  end,  and  the  opening  of  the  water- 
vascular  system  at  the  posterior  end,  are  readily  seen.  Compress 


TETEASTEMMA.  49 

slightly  if  the  trunks  of  the  water-vascular  system  are  not  easily 
seen.  They  can  always  be  seen  in  preserved  and  stained  speci- 
mens that  have  been  killed  under  pressure.  If  you  have  trouble 
in  seeing  them,  examine  such  a  specimen.  Do  you  find  pro- 
glottids?  Understand  the  relation  of  this  larva  to  a  true  cysti- 
cercoid. 

Curtis:  Crossobothrium  laciniatum  and  Developmental  Stimuli  in  the 

Cestoda.    Biol.  Bui.,  5,  1903. 
:  The  Formation  of  Proglottids  in  Crossobothrium  laciniatum.    Biol. 

Bui.,  11,  1906. 
Linton:  A  Cestode  Parasite  in  the  Flesh  of  the  Butterfish.    Bui.  U.  S. 

Bur.  Fish.,  26.  1906. 
Tennent:  A  Study  of  the  Life-history  of  Bucephalus  haimeanus:  A  Parasite 

of  the  Oyster.    Quart.  Jour.  Mic.  Sci.,  49,  1906. 


NEMERTINEA. 

Several  representatives  of  this  group  are  rather  easily  ob- 
tained. Some  of  these,  as  some  species  of  Cerebratulus  and 
Meckelia,  are  large,  but  they  are  generally  unsatisfactory  for 
anatomic  study,  as  they  are  opaque  and  filled  with  a  connective- 
tissue  parenchyma  that  binds  the  organs  together.  Further- 
more, they  are  especially  likely  to  cut  themselves  into  small 
pieces  by  contraction  of  muscles  in  the  body-wall. 

TETRASTEMMA. 

This  small  animal  lives  among  the  forms  that  are  generally 
found  attached  to  piles.  Specimens  can  usually  be  found  by  plac- 
ing scrapings  from  piles  in  a  glass  jar  with  a  little  sea-water  and 
allowing  them  to  stand  from  a  half  hour  to  three  hours.  The 
animals  may  then  be  found,  with  the  aid  of  a  lens,  on  the  sides 
of  the  dish,  usually  near  the  surface. 

With  a  pipet  transfer  a  specimen  to  a  slide,  cover  it,  and 
examine  with  low  and  high  powers  of  the  microscope.  Notice : 

1.  The  shape  of  the  body,  the  four  eye-spots,  and  the  ciliated 
grooves. 

2.  The  straight  alimentary  canal.    The  diverticula  of  the 
intestine  and  the  terminal  anus. 

4 


50  PLATYHELMINTHES. 

3.  The  enormous  proboscis,  consisting  of  a  large  anterior 
eversible  portion,  and  a  smaller  posterior  portion  that  is  not 
eversible.     When  the   proboscis   is   retracted  it   is  bent  upon 
itself.     Stylets  are  present  in  the  eversible  portion,  near  its 
inner  end.     Can  you  determine  how  the  proboscis  is  protruded 
and  retracted?    Does  the  proboscis  have  anything  to  do  with 
the  digestive  system? 

4.  Beneath  the  posterior  eye-spots  are  the  cerebral  ganglia, 
from  which  lateral  nerve  cords  extend  posteriorly. 

5.  If  the  specimen  happens  to  contain  eggs,  they  will  lie 
between  the  diverticula  of  the  intestine.    They  are  compara- 
tively very  large. 

Coe:  Development  of  the  Pilidium  of  Certain  Nemerteans.    Trans.  Conn. 

Acad.,  10,  1899. 
:  On  the  Anatomy  of  a  Species  of  Nemertean  (Cerebratulus  lacteus). 

Trans.  Conn.  Acad.,  10,  1890. 
Verrill:  The  Marine  Nemerteans  of  New  England  and  Adjacent  Waters. 

Trans.  Conn.  Acad.  Sci.,  8,  1892. 
C.  B.  Wilson:  Habits  and  Early  Development  of  Cerebratulus  lacteus. 

Quart.  Jour.  Mic.  Sci.,  43,  1900. 


NEMATHELMINTHES. 

Body  elongated,  cylindrical,  and  not  segmented.  Many  are 
parasitic  forms.  Anus  usually  present.  Coelom  not  filled  with 
parenchyma.  The  classes  may  not  be  genetically  related. 

CLASS  1.  Nematoda. 

Many  are  internal  parasites,  but  others  are  found 
in  fresh  and  salt  water  and  in  damp  earth.  Body 
pointed  at  both  ends.  Mouth  terminal,  anus  ven- 
tral. (Ascaris,  Trichina,  Gordius.) 

CLASS  2.  Acanthocephala. 

Formidable  intestinal  parasites.  Proboscis  bearing 
hooks.  No  alimentary  canal.  (Echinorhynchus.) 

CLASS  3.  Chsetognatha. 

Marine,  and  all  but  one  species  pelagic.  With  caudal 
and  lateral  fins  and  bristle-like  jaws.  (Sagitta.) 

ASCARIS. 

Animals  belonging  to  this  genus  are  common  in  the  intestine 
of  the  horse  and  pig,  and  are  not  uncommon  in  man.  Examine 
specimens  and  see  if  they  have  any  organs  that  would  aid  them  in 
clinging  to  the  intestinal  wall.  How  can  they  retain  their  positions  ? 

1.  Can  you  determine  which  is  anterior  and  which  is  posterior? 
Is   there   any   indication   of   segmentation?    Can   the   ventral 
side  be  told  from  the  dorsal? 

2.  Find  the  mouth  and  see  that  it  is  bounded  by  three  lips. 
Notice  how  these  are  placed  and  find  the  papillae  on  the  ventral 
ones.     Find  the  anus  and  note  its  position.     This  serves  also  as 
a  reproductive  aperture  for  the  male.     In  the  female  the  repro- 
ductive aperture  is  situated  about  one-third  back   from   the 
anterior  end.     It  can  be  seen  only  in  favorable  specimens. 

51 


52  NEMATHELMINTHES. 

3.  Open  a  well  preserved  or  fresh  specimen  along  the  dor- 
sal line  and  notice  the  definite  codom,  and  the  straight  alimentary 
canal.  If  the  specimen  is  a  female,  find  the  Y-shaped  genital 
organs,  the  free,  ovarian  ends  of  which  are  slender  and  some- 
what tangled.  The  position  of  the  external  genital  opening  has 
already  been  noted.  In  the  male  there  is  a  single,  tangled,  thread- 
like testis,  which  joins  the  enlarged  seminal  vesicle  that  extends 
to  the  cloaca.  The  nervous  system  consists  of  a  circum-esopha- 
geal  ring,  six  longitudinal  nerves,  the  dorsal  and  ventral  of 
which  are  larger  than  the  others,  and  anterior  nerves.  It  is 
not  easily  seen. 

A  drawing  is  desirable. 

Montgomery :  The  Adult  Organization  of  Paragordius  varius.    Zool.  Jahrb., 
18,  1903. 

TRICHINA. 

Encysted  specimens  may  frequently  be  found  by  examining 
thin  pieces  of  pig  muscle  obtained  from  the  meat  market.  Pigs 
fattened  in  small  pens  and  fed  on  table  waste,  or  in  slaughter- 
yards  and  fed  on  the  offal  of  butchered  animals,  are  much 
more  likely  to  be  infected  than  others.  Scavenger  rats  and 
cats  are  frequently  infected. 

1.  Flatten  a  piece  of  muscle  containing  trichinae  between 
two  slides  in  a  little  glycerin  and  notice  the  relation  of  the  ani- 
mal to  the  muscle  fibers.     Notice  the  cyst  that  surrounds  it 
and  see  if  you  can  determine  whether  this  was  formed  by  the 
host  or  the  parasite.     There  are  frequently  fat  cells  at  the  ends 
of  the  cyst.     Just  after  the  parasites  are  encysted,  the  cysts  are 
surrounded  by  capillaries  that  may  be  injected  by  injecting  the 
vessels  of  the  host.     These  may  be  found  only  at  a  definite  stage 
after  encystment.     Why  are  they  formed?    Do  they  indicate 
how  the  cysts  were  formed?    If  the  trichinae  are  abundant  see 
if  you  can  find  more  than  one  in  a  cyst. 

2.  Notice  the  shape  that  is  assumed  by  the  parasite.     Is 
the  coiling  always  the  same?    If  your  material  is  fresh,  mount 
some  of  fhe  muscle  between  slides  without  glycerin,  warm  the 
slide,  and  see  if  the  encysted  animals  will  move. 


TRICHINA.  53 

3.  Are  the  anterior  and  posterior  ends  alike?  Is  there  any 
indication  of  a  mouth?  The  large  cells  that  form  the  intestine 
can  frequently  be  seen.  It  should  be  borne  in  mind  that  the 
encysted  specimen  is  not  fully  adult  and  that  the  animal  grows 
after  reaching  the  alimentary  canal  of  the  next  host. 

Make  a  drawing  of  an  encysted  animal. 

Glazier:  Report  on  Trichinae  and  Trichinosis.     U.  S.  Treas.  Dept.  Doc. 
No.  84,  Marine  Hospital,  1881. 


TRCXHELRHNTHES. 

Minute  animals  whose  adult  structure  seems  to  be  related  to 
that  of  the  trochophore  larva.  Mouth  usually  surrounded  by  a 
circlet  of  cilia.  Three  classes  (Rotifera,  Dinophilea,  and  Gastro- 
tricha)  are  referred  to  this  phylum,  but  they  may  not  be  geneti- 
cally related. 

ROTIFERA. 

Mostly  fresh-water  forms,  but  a  few  are  marine.  All  are  of 
microscopic  size.  The  pharynx  is  provided  with  a  masticatory 
apparatus,  and  the  anterior  end  bears  a  trochal  disk.  Most 
rotifers  are  free,  but  a  few  are  permanently  attached,  and  some, 
as  Melocerta,  live  in  tubes  of  their  own  formation. 

BRACHIONUS  (A  Rotifer). 

These  animals  are  frequently  quite  abundant  in  ponds  and 
aquaria.  They  are  not  very  active,  and  spend  most  of  their 
time  near  the  bottom  among  the  plants  and  debris.  Owing 
to  their  minute  size,  they  must  be  studied  with  a  high  power 
of  the  microscope. 

1.  The  body  is  divided  into  a  trunk,  which  is  inclosed  in  a 
transparent  cuticular  lorica,  and  a  movable  tail  or  foot.    The 
tail  is  tipped  with  two  processes  which  form  forceps,  by  means 
of  which  it  attaches  itself  to  plants.     Can  you  see  how  these  are 
used?    Why  does  the  animal  need  to  attach  itself? 

2.  Projecting   anteriorly  from  the   lorica   is  the   retractile 
trochal  disk.     Notice  the  cilia  on  the  margin  of  this  disk.     Is 
the  disk  used  in  locomotion?    Does  the  animal  always  move 
when  the  cilia  are  active  ?    What  other  use  has  the  disk  ?     Is  the 
animal  entirely  dependent  upon  the  cilia  of  the  disk  for  loco- 
motion? 

54 


BRACHIONUS.  55 

3.  The  mouth  is  at  the  ventral  border  of  the  trochal  disk  and 
leads  by  a  short  buccal  cavity  to  the  mastax,  which  is  a  muscu- 
lar apparatus  provided  with  three  chitinous  trophi  (a  median 
incus  and  two  mallei).     It  is  used  in  grinding  the  food.    The 
grinding  movements  are  easily  seen.    A  very  short  gullet  leads 
from  the  mastax  to  the  large  stomach.     The  intestine  is  short 
and  thick  and  opens  into  a  cloaca.    The  anus  is  near  the  base 
of  the  tail,  on  the  dorsal  surface. 

4.  The  reproductive  and  excretory  systems  are  not  easily 
seen.    An  ovary  and  a  large  vitellarium  are  present.     The  ovi- 
duct opens  into  the  cloaca.     Two  long  nephridial  tubes  open  into 
a  contractile  vesicle  that  in  turn  opens  into  the  cloaca. 

5.  There  is  a  single  ganglion  in  the  anterior  dorsal  region, 
immediately  beneath  two  red  eye-spots.    Anterior  to  the  eye- 
spots  is  a  dorsal  feeler,  which  is  a  tactile  organ. 

There  are  many  common  rotifers  that  have  no  lorica  and 
some  of  them  have  the  trochal  disk  two-lobed. 

Jennings:  Rotatoria  of  the  United  States  with  Especial  Reference  to  those 

of  the  Great  Lakes.     Bui.  U.  S.  Fish  Com.,  19,  1899. 
Whitney:  The  Desiccation  of  Rotifers.    Am.  Nat.,  42,  1908. 


MOLLUSCOIDA. 

Lophophore  present.    Mouth  and  anus  closely  approximated. 
Ccelom  usually  present. 

CLASS  1.  Polyzoa. 

Usually  colonial.     Zooids  of  small  size  and  pro- 
tected by  a  firm  cuticle. 
Subclass  1.  Ectoprocta. 

Anus  outside  of  the  lophophore. 

Order  1.  Gymnolaemata. 

Marine.      Circular    lophophore.      No   epistome 
present.     (Bugula,  Membranipora.) 

Order  2.  Phylactolsemata. 

Fresh -water.      Horseshoe -shaped     lophophore. 
Epistome  present.     (Plumatella,  Pectinatella.) 
Subclass  2.  Endoprocta. 

Colonial  or  solitary.    Anus  and  mouth  both  in- 
side of  the  lophophore.    (Loxosoma,  Pedicellina.) 
CLASS  2.  Phoronida. 

Marine.   Solitary.   Lophophore  horseshoe-shaped 
with  each  end  coiled.     (Phoronis.) 
CLASS  3.  Brachiopoda. 

Marine.    Solitary.     Bivalve   shell.    Usually  at- 
tached by  a  peduncle. 

Order  1.  Inarticulata. 

Valves  not  united  by  a  hinge.     (Lingula.) 

Order  2.  Articulata. 

Valves  hinged.     Usually  with  a  shelly  loop  to 
support  the  lophophore.     (Terebratulina.) 


POLYZOA; 

BUGULA. 

The  colonies  are  very  common  in  shallow  water  along  shore, 
attached  to  rocks  and  piles.  They  may  be  examined  with  the 
aid  of  a  glass-bottomed  pail  in  the  positions  they  occupy  on  the 

56 


BUGULA.  57 

sides  of  the  piles  of  almost  any  old  wharf.  What  must  be  the 
source  of  their  food?  What  part  of  the  colony  is  likely  to  be 
best  nourished?  Collect  specimens  by  scraping  the  piles  and 
see  what  forms  are  associated  with  them. 

1.  Examine   a  colony  in  a  dish  of  water  and  see  how  it 
branches.    Does  it  present  any  regularity? 

Make  a  drawing  of  a  colony. 

2.  Remove  one  of  the  flat  branches,  place  it  in  a  watch-glass 
of  water,  and  examine  it  with  a  low  power.     What  more  can  be 
observed  regarding  the  branches?    How  are  the  cups  arranged? 
Are  the  cups  on  the  two  sides  of  a  twig  placed  in  definite  rela- 
tions to  each  other?    Where  are  the  empty  cups  found?    Why? 
Can  you  find  connections  between  the  cups  of  the  two  sides? 

Make  a  drawing  showing  the  arrangement  of  the  cups. 

3.  Allow  a  living  branch  to  remain  undisturbed  for  a  few 
moments  and  with  a  microscope  see  how  the  thin  outer  mar- 
gins of  the  cups  are  unfolded  as  the  zooids  protrude. 

4.  Mount  a  specimen  on  a  slide,  cover,  and  compare  the 
tentacles  of  an  expanded  zooid  with  those  of  the  hydroids  that 
you  studied.    How  do  they  differ?    How  must  the  animal  feed? 

5.  How  are  the  tentacles  arranged  around  the  distal  end  of 
the  body?    How  many  tentacles  are  there ?    Look  for  the  mouth. 

6.  Can  you  see  the  parts  of  the  alimentary  canal?     Is  there 
food  in  the  stomach  ?    How  does  the  zooid  pull  itself  back  into 
its  cup? 

7.  Look  for  avicularia  and  observe  their  movements  and 
structure.    Where  is  the  jaw  hinged?    Where  are  the  muscles 
that  open  it?    Where  are  the  muscles  that  close  it?    Of  these 
muscles,  which  are  largest?    Why?    See  if  " sense  hairs"  can 
be  found  between  the  jaws.     What  is  their  probable  use? 

Draw  an  avicularium. 

8.  Ooecia  with  embryos  will  be  found  in  some  specimens. 
Where  are  they  placed? 

9.  Put  powdered  carmine  in  the  water  with  a  living  branch 
and  see  if  the  zooids  will  eat  it. 

10.  Put  a  small  living  branch  in  a  drop  of  sea-water  under 
a  supported  cover-glass  and  see  if  any  of  the  zooids  will  expand. 


58  MOLLUSCOIDA. 

If  any  do  expand  they  may  be  examined,  with  a  high  power, 
to  good  advantage. 

Study  specimens  that  have  been  killed  while  expanded. 
Stain  with  iodin,  wash  in  water,  mount  in  glycerin,  study  with 
a  high  power.  Find  the  retractor  muscles,  the  funiculus,  germ 
cells,  and,  if  possible,  the  shape  of  the  alimentary  canal.  As 
the  alimentary  canal  bears  a  definite  relation  to  the  position 
of  the  zooid  on  the  branch,  its  shape  can  be  readily  determined 
only  when  the  branch  happens  to  be  twisted  so  the  zooid  is 
to  be  seen  in  side  view. 

Make  a  drawing  showing  the  structure. 

If  time  permits  it  will  be  desirable  to  examine  an  incrusting 
form  to  determine  its  method  of  branching  and  the  way  in  which 
the  cups  are  closed. 

Nitsche:  Beitrage  zur  Kenntnis  der  Bryozoen.  Ueber  die  Anatomic  und 
Entwicklungsgeschichte  von  Flustra  membranacea.  Zeit.  f.  Wiss. 
ZooL,  21,  1871. 

PLUMATELLA.1 

If  the  zooids  of  this  fresh-water  form  will  expand  in  a  watch- 
glass  of  fresh  water,  notice  the  shape  of  the  lophophore  and  the 
position  of  the  epistome.  In  such  a  specimen  the  ganglion  may 
be  seen  as  a  rounded  mass  just  beneath  the  lophophore,  between 
the  mouth  and  the  anus.  Study  the  statoblasts  with  a  micro- 
scope. 

Allman:  Monograph  of  the  Fresh-water  Polyzoa.    Ray  Soc.,  1856. 
BRACHIOPODA. 

TEREBRATULINA. 

Examine  specimens  on  the  demonstration  table  and  notice : 
1.  Shell.    The  difference  in  the  size  and  shape  of  the  two 

valves  and  their  position  in  relation  to  the  body.     How  are  the 

valves  articulated?    How  are  they  opened? 

1  Slices  of  the  large  gelatinous  form,  Pectinatella,  placed  in  watch- 
glasses  of  fresh  water,  make  very  satisfactory  objects  for  study,  as  the 
zooids  will  soon  expand,  and  they  are  then  hi  the  best  possible  position  for 
study. 


TEREBRATULINA.  59 

2.  Peduncle.    Its  position.     What  is  its  use? 

3.  Muscles.    Those  used  in  opening  and  closing  the  shell. 

4.  Lophoph&re.     Consisting  of  two  elongated  arms  with  a 
double  row  of  tentacles  on  each. 

5.  Mouth.    Notice  its  relation  to  the  grooves  running  be- 
tween the  rows  of  tentacles  on  each  of  the  arms  of  the  lophophore. 

Brooks:  Development  of  Lingula.     Ches.  Zool.  Lab.  Sci.  Results,  1878. 
Conklin:  The  Embryology  of  a  Brachiopod,  Terebratulina  septentrionalis. 

Proc.  Am.  Phil.  Soc.,  41,  1902. 
Hancock :  On  the  Organization  of  Brachiopoda.     Trans.  Roy.  Soc.,  London. 

148,  1858. 
Morse:  Observations  on  Living  Brachiopoda.     Mem.  Bost.  Soc.  Nat.  Hist., 

5,  1902. 


ECHINODERMATA. 

Radially  symmetrical  animals,  with  calcareous  plates  in  the 
integument.     Water-vascular  system  always  present. 

CLASS  1.  Asteroidea. 

With  radiating  arms  not  sharply  defined  from 

the  central  disk.    Ambulacral  feet  in  grooves 

on  the  oral  side. 
Order  1.  Phanerozonia. 

With  large  marginal  ossicles.     (Astropecten.) 
Order  2.  Cryptozonia. 

Marginal  ossicles  inconspicuous.     (Asterias.) 
CLASS  2.  Ophiuroidea. 

With   slender   radiating   arms   sharply   defined 

from  the  central  disk.     No  ambulacral  grooves. 
Order  1.  Ophiurida. 

Arms  not  branched.     (Ophiura.) 
Order  2.  Euryalida. 

Arms  branched.     (Astrophyton.) 
CLASS  3.  Echinoidea. 

Globular,  or  somewhat  disk-shaped,  spiny  bodies. 

Shell  or  test  composed  of  close-fitting  plates. 
Order  1.  Regularia. 

Nearly    globular    test.      Spines    rather    large. 

Mouth   and    anus   polar.     Jaws   present.     (Ar- 

bacia,  Strongylocentrotus.) 
Order  2.  Clypeastroidea. 

More  or  less  flattened  test.     Spines  very  small. 

Anus  not  polar.     Jaws  present.     (Echinarach- 

nius.) 
Order  3.  Spatangoidea. 

Somewhat  flattened  and  elongated.     Spines  very 

small.     Neither  mouth  nor  anus  polar. 
CLASS  4.  Holothuroidea. 

Bodies  soft,  elongated  and  cylindrical.     Mouth 

and  anus  polar,  the  former  surrounded  by  a  cir- 
clet of  large  oral  tentacles. 
60 


ASTEKIAS.  61 

Order  1.  Elasipoda. 

Well-marked  bilateral  symmetry.    Tube  feet  on 

ventral  and  papillae  on  dorsal  surface.     Deep 

sea  only. 
Order  2.  Pedata. 

Ambulacral  feet  in  rows  or  scattered.     (Thyone, 

Cucumaria.) 
Order  3.  Apoda. 

Without  tube  feet.     Worm-like.     (Synaptula.) 
CLASS  5.  Crinoidea. 

Temporarily    or    permanently    attached    by    a 

stalk.     With    five    branching    arms    radiating 

from  a  small  disk. 
Order  1.  Neo-Crinoidea. 

Characters  as  above.     (Antedon,  Pentacrinus.) 

Berry:  Metamorphosis  of  Echinodenns.     Quart.  Jour.  Mic.  Sci.,  38,  1905. 
Grave:  Occurrence  among  Echinodenns  of  Larvae  with  Cilia  Arranged  in 
Transverse  Rings.     Biol.  Bui.,  5,  1903. 


ASTEROIDEA:    ^ 

ASTERIAS.     (Starfish.) 

Starfishes  are  rather  common  along  most  coasts  and  are 
among  the  worst  enemies  of  oysters.  They  can  generally  be 
most  satisfactorily  examined  on  shallow-water  mussel-beds  or 
on  rocks  covered  with  barnacles.  Places  where  starfish  occur 
should  be  visited,  and  the  conditions  under  which  they  live  ex- 
amined. Determine : 

1.  Upon  what  and  how  they  feed. 

2.  What  their  enemies  must  be. 

3.  How  their  arms  are  repaired  when  injured.     Do  you  find 
specimens  that  are  growing  new  tips  to  injured  arms  or  are  such 
arms  apparently  replaced  ?    When  an  arm  is  injured  how  must 
the  animal  proceed  to  repair  it? 

4.  Do  specimens  ever  conceal  themselves?    See  if  specimens 
can  be  found  with  pieces  of  grass  and  weeds  covering  them. 
Try  picking  these  pieces  off  to  see  if  they  adhere. 

5.  Do  the  animals  have  other  means  of  protection? 
Examine  a  specimen  and  notice: 

1.  That  the  surface  by  which  the  animal  clings,  the  oral 


62  ECHINODEEMATA. 

surface,  is  different  from  the  other,  aboral  surface,  and  that 
both  surfaces  are  covered  with  short  spines.  What  is  the  use 
of  the  spines? 

2.  It  consists  of  radiating  arms  and  a  central  disk. 

3.  On  the  aboral  surface  of  the  disk,  near  the  junction  of  the 
two  arms,  a  small,  frequently  conspicuously  colored,  circular  body, 
the  madreporic  plate.    The  two  arms  adjacent  to  this  plate  are 
sometimes  referred  to  as  the  bivium,  and  the  remaining  three  as 
the  trivium.    The  radial  symmetry  of  the  animal  is  disturbed  ex- 
ternally only  by  the  madreporic  plate.    Examine  this  plate  with 
a  lens  and  determine  its  structure. 

4.  On  the  oral  surface,  the  mouth.    Note  its  size  and  see  if 
it  is  provided  with  jaws  of  any  kind.     Would  you  expect  jaws? 
Why? 

5.  Radiating  from  the  mouth  are  the  ambulacral  grooves, 
one  on  each  arm.     In  these  grooves  are  the  ambulacral  or  tube 
feet.    Do  they  have  a  definite  arrangement?    Along  the  sides 
of  the  grooves  are  slender  spines  that  differ  from  the  general 
body-spines  in  being  movable. 

6.  Scrape  the  tube  feet  from  a  portion  of  an  ambulacral  groove 
of  a  dried  specimen  and  notice  the  pores  through  which  the  feet 
are  attached  to  organs  inside  the  arm.     Notice  also  the  exposed 
ambulacral  plates  and  determine  their  relation  to  the  pores. 

Draw  figures  of  the  aboral  and  oral  surfaces  of  a  starfish,  and  a 
diagram  to  show  the  relation  of  the  ambulacral  plates  and  pores. 
Place  a  living  starfish  in  a  dish  of  sea-water. 

1.  Study  its  method  of  locomotion.     How  are   the   ambu- 
lacral feet  used?    How  far  can  they  be  protruded? 

2.  Tear  the  starfish  quickly  from  the  bottom.     Do  any  of 
the  feet  remain  behind  ?    Understand  how  they  are  attached. 

3.  Place  the  starfish  on  its  aboral  surface  and  watch  it  turn 
over. 

4.  Find  the  thread-like  dermal  branchice  projecting  through  the 
body  integument.    Are  they  withdrawn  when  touched?    What 
is  their  function? 

5.  Stroke  the  starfish  with  a  camel 's-hair  brush  and  notice 
how  the  hairs  are  caught.    Can  you  determine  by  what  and 


ASTEEIAS.  63 

how  they  are  held?  With  a  hand-lens  examine  around  the  bases 
of  the  spines,  and  see  the  arrangement  of  the  pedicellarice.  Their 
function  is  obscure,  but  they  enable  the  starfish  to  hold  small 
objects  firmly  and  they  may  be  of  service  in  dealing  with  possi- 
ble surface  parasites. 

6.  Remove  some  of  the  pedicellarice  with  a  scalpel  and  ex- 
amine them  under  the  microscope.  Is  there  more  than  one  kind? 

Draw  a  pedicellaria. 

Internal  Structure. — Make  the  dissection  under  water,  and  in 
cutting  through  the  integument  be  careful  not  to  injure  the 
underlying  soft  parts. 

With  strong  scissors  cut  through  the  aboral  body-wall  near 
the  tips  of  the  rays  of  the  trivium.  Carry  the  cuts  forward 
along  the  sides  of  the  rays  to  the  disk.  The  cavity  thus  opened 
is  the  ccelom  or  body  cavity. 

Lift  up  the  integument  at  the  tip  of  each  arm  and  carefully 
snip  away  the  mesenteries  which  attach  the  organs  to  it.  Cut 
the  membranes  that  extend  into  the  disk  opposite  the  junc- 
tions of  the  arms,  and  remove  the  three-rayed  flap  of  integu- 
ment thus  freed,  cutting  as  close  as  possible  to  the  madreporite, 
but  leaving  this  in  place. 

Digestive  System. — In  studying  this  system  you  should  con- 
stantly bear  in  mind  the  peculiar  method  by  which  the  animal 
feeds,  as  the  digestive  system  is  highly  modified  to  suit  this 
method. 

1.  The  short,  cone-shaped  intestine  and  the  intestinal  cceca 
were  probably  removed  with  the  integument.    The  intestine 
probably  does  not  function,  and  may  be  regarded  as  a  vestige. 
It  opens  near  the  center  of  the  disk,  on  the  aboral  side,  by  a 
very  minute  anus  that  is  very  hard  to  see. 

2.  The  stomach,  which  occupies  the  greater  part  of  the  space 
in  the  disk,  is  composed  of  a  small  aboral  portion,  the  pyloric 
division,  that  receives  the  ducts  from  the  hepatic  caeca,  and  a 
larger,  lobed,  cardiac  division,  into  which  the  mouth  opens. 
The  cardiac  portion  may  be  everted  through  the  mouth,  thus 
being  turned  wrong  side  out.     Five  pairs  of  muscles,  which  draw 
this  portion  of  the  stomach  back  into  place,  may  be  seen  at- 


64  ECHINODERMATA. 

tached  to  the  ridges  formed  by  the  ambulacral  plates  in  each  arm. 
How  is  it  possible  for  the  stomach  to  be  everted?  What  reason 
is  there  for  two  divisions? 

3.  In  each  arm  is  a  pair  of  long,  glandular  organs,  the  hepatic 
cceca.  The  ducts  of  each  pair  unite  and  join  the  pyloric  divi- 
sion of  the  stomach  by  a  common  duct.  These  are  digestive 
glands.  What  reason  is  there  for  having  ten  enormous  digestive 
glands?  Does  this  have  anything  to  do  with  the  method  of  feed- 
ing? 

Make  a  drawing  of  the  digestive  system  of  the  disk  and  one 
arm. 

Reproductive  System. — Turn  the  hepatic  caeca  to  one  side  and 
notice  the  ovaries  or  testes.  The  sexes  are  separate,  but  the 
organs  have  the  same  general  appearance  in  both  sexes.  They 
vary  in  size  according  to  the  season  of  the  year,  sometimes 
being  so  small  that  they  are  not  easily  found,  and  again  being 
nearly  or  quite  as  large  as  the  hepatic  caeca.  With  a  pair  of 
forceps  lift  up  one  of  these  organs  and  see  where  it  is  attached. 
It  is  at  this  point  that  the  reproductive  cells  reach  the  exterior. 
How  many  gonads  are  there  ? 

Draw  the  gonads  into  another  arm  of  your  figure. 

Water-vascular  System.1—!.  Carefully  remove  the  side  of  the 
stomach  next  to  the  bivium,  being  very  careful  not  to  disturb 
the  stone  canal,  which  runs  from  the  madreporic  plate  to  the 
margin  of  the  membrane  around  the  mouth.  By  the  side  of 
the  stone  canal  is  a  thin  band  of  tissue  formerly  supposed  to  be  a 
heart.  It  is  now  generally  believed  to  be  connected  with  the 
reproductive  system,  and  is  frequently  referred  to  as  the  axial 
organ.  It  has  nothing  to  do  with  the  system  now  under  con- 
sideration. 

2.  The  circular  canal,  which  is  joined  by  the  stone  canal  at 
the  outer  margin  of  the  peristomial  membrane,  follows  the  mar- 
gin of  the  membrane  and  so  encircles  the  mouth.  Originating 

1  This  may  be  injected  in  fresh  specimens,  either  with  gelatin  or  fine 
starch-mass,  by  picking  up  one  of  the  radial  canals  with  a  hypodermic 
syringe  and  injecting  toward  the  disk. 


ASTERIAS.  65 

from  it  at  points  very  near  the  ampullae  of  the  first  tube  feet 
are  nine  small  vesicles,  Tiedemann  bodies.  They  are  smaller 
than  the  ampullae  and  project  in  toward  the  mouth.  The  posi- 
tion where  the  tenth  Tiedemann  body  might  be  expected,  is 
taken  by  the  stone  canal. 

3.  Leaving  the  circular  canal   are  five  radial  water  tubes, 
one  for  each  arm.     These  tubes  lie  along  the  oral  surfaces  of 
the  ambulacral  plates,  and  are  accordingly  not  visible  on  the 
inside  of  the  animal.    The  position  of  the  tube  can  best  be 
understood  by  making  a  transverse  section  of  an  arm.     It  will 
then  be  seen  either  in  injected  or  uninjected  specimens,  lying 
immediately  below  the  ambulacral  plates.     In  injected  speci- 
mens it  may  be  followed  by  dissecting  from  the  oral  side,  from 
the  circular  canal  to  the  extremity  of  the  arm,  where  it  ends 
in  a  small  tentacle. 

4.  Along  the  sides  of  the  ambulacral  ridges,  within  the  body- 
cavity,  are  rows  of  little  bag-like  ampullce.     Determine  their  re- 
lation to  the  ambulacral  pores.     If  the  specimen  is  fresh,  press  a 
few  ampullae  and  see  if  the  corresponding  tube  feet  are  affected. 
Can  you  determine  their  function  ?     In  a  dissection  it  is  hard  to 
find  the  connecting  tubes  that  join  the  radial  tubes  to  the  tube 
feet,  but  they  can  sometimes  be  seen  in  sections  of  arms  of 
injected  specimens.    They  can  readily  be  seen  in  microscopic 
preparations. 

The  water-vascular  system  is  very  distinctive  for  the  Echi- 
nodermata,  and  you  should  understand  perfectly: 
(a)  How  the  tube  feet  are  extended. 
(6)  What  causes  them  to  adhere. 

(c)  The  connection  between  tube  feet,  ampullae,  connecting 
canals,  radial  water  tubes,  circular  canal,  stone  canal,  and  mad- 
reporic  plate. 

(d)  How  it  is  possible  to  extend  one  foot  without  extend- 
ing others. 

Make  a  drawing  showing  the  arrangement  of  the  water-vascu- 
lar system, 

Nervous  System. — This  is  not  easily  studied  by  dissection. 
5 


66  ECHINODERMATA. 

It  consists  of  a  nerve  ring  which  encircles  the  mouth  and  lies 
just  ventral  to  the  circular  water  canal,  and  five  radial  nerves 
that  extend  down  the  arms  just  beneath  the  radial  water  tubes, 
to  end  at  the  tips  of  the  arms  in  pigment  spots,  the  eye- 
spots.  The  whole  central  nervous  system  is  superficial  and  forms 
a  portion  of  the  outer  covering  of  the  body.  The  radial 
nerves  can  be  seen  by  separating  the  rows  of  ambulacral  feet, 
but  it  is  much  more  satisfactory  to  study  them  in  prepared 
sections. 

Muscular  System. — Examine  the  walls  of  the  starfish  for 
its  muscular  system.  If  time  permits,  it  will  be  desirable  to 
macerate  a  portion  of  an  arm  to  see  the  skeleton  to  which  these 
muscles  are  attached. 

Study  prepared  sections  of  the  arm  of  a  small  starfish  and 
determine  the  relation  of  organs. 

1.  The   hepatic    caeca.     How   are   they   supported?    What 
is  their  structure  ? 

2.  The  radial  canal,  connecting  tubes,  tube  feet,  and  ampullae. 

3.  The  thickened,  deeply  stained,  radial  nerve  between  the 
tube  feet  and  below  the  radial  water  tube. 

4.  The  perihaemal  canal,  divided  by  a  thin  partition,  that  lies 
between  the  radial  water  tube  and  the  radial  nerve. 

Make  a  drawing  of  a  section  of  an  arm  that  will  show  these 
points. 

Understand  how  a  starfish  can  open  an  oyster  or  a  mussel 
and  how  it  digests  it  when  open.  How  can  it  digest  a  barnacle 
or  a  small  snail  ?  How  does  it  respire  ? 

Field:  Larva  of  Asterias  yulgaris.     Quart.  Jour.  Mic.  Sci.,  34,  1892. 
Goto:  The  Metamorphosis  of  Asterias  pallida,  with  Special  Reference  to  the 

Fate  of  the  Body  Cavities.     Jour.  Col.  Sci.  Imp.  Univ.,  Tokyo,  10,  1898. 
Harvey:  Methods  of  Artificial  Parthenogenesis.     Biol.  Bui.,  18,  1910. 
Jennings:  Behavior  of  the  Starfish  Asterias  forreri.     Univ.  Calif.  Pub. 

Zool.,  4,  1907. 
Mead:  The  Natural  History  of  the  Star-fish.    Bui.  U.  S.  Fish  Com.,  1899. 


OPHIUBOIDEA.  67 


OPHIUROIDEA. 

OPHIURA.    (Serpent-Star.) 

These  animals  live  more  or  less  concealed  in  crevices,  shells, 
eel-grass,  etc.,  and  may  be  obtained  either  by  dredging  or  by 
pulling  a  dip-net  through  eel-grass.  They  are  not  conspicuous 
objects  along  the  shore,  as  are  starfish,  and  they  differ  essen- 
tially from  starfish  in  their  method  of  locomotion  and  their 
method  of  feeding. 

Examine  a  specimen  and  notice : 

1.  The  appearance  of  the  disk  and  arms.    Are  the  spines 
similar  to  those  of  Asterias?    The  arms  are  more  flexible.     In 
what  direction  do  they  bend  easiest  ? 

2.  The  five  buccal  plates,  one  of  which  bears  a  madreporic 
opening  that  is  not  easily  seen. 

3.  The  size  and  shape  of  the  mouth. 

4.  The  ambulacral  groove.     Is  it  distinct? 

5.  The  ambulacral  feet.    Do  they  have  suckers?    How  are 
they  arranged? 

6.  The  openings  to  the  bursse,  near  the  bases  of  the  arms. 
Most  Ophiurians  have  five  pairs  of  these  openings,  one  for  each 
bursa,  but  Ophiura  has  ten  pairs,  two  for  each  bursa. 

Draw  an  oral  view  of  a  specimen. 

Place  a  living  specimen  in  a  dish  of  sea-water  and  watch  its 
movements. 

1.  Compare  the  rate  and  method  of  movement  with  Asterias. 

2.  Are  all  of  the  arms  used  in  progressing  in  the  same  way? 

3.  See  if  the  arms  can  be  used  interchangeably  or  if  a  cer- 
tain one  is  always  directed  forward. 

4.  Are  the  ambulacral  feet  of  any  service?    Do  they  adhere? 
The  internal  structure  shows  that  the  stomach  is  not  eversible 
and  that  the  hepatic  caeca  do  not  extend  into  the  arms.     Is 
there  any  correlation  between  these  two  facts? 

The  nervous  and  water-vascular  systems  are  very  similar 
to  those  of  Asterias,  but  here  the  former  lies  within  instead  of 


68  ECHINODERMATA. 

on  the  surface  of  the  arm,  the  entire  arm  being  encased  with 
four  or  more  rows  of  shields.  They  can  be  studied  best  in 
sections. 

Grave:  Ophiura  brevispina.     Mem.  Biol.  Lab.  Johns  Hopkins  Univ.,  4, 
1900.    Mem.  Nat.  Acad.,  8,  1899. 


ECHINOIDEA. 
STRONGYLOCENTROTUS.1  (Sea-Urchin.) 

In  some  localities  sea-urchins  can  be  found  in  tide  pools 
or  near  low-tide  mark,  where  they  may  be  very  abundant.  In 
other  localities  they  can  be  obtained  only  by  dredging.  When 
possible  they  should  be  observed  in  their  native  places  and  the 
conditions  noted. 

1.  What  apparently  serves  as  food  for  the  animal?    Can  you 
determine  how  this  is  obtained? 

2.  Do  you  find  attempts  at  concealment? 

3.  Are  the  animals  able  to  climb? 

Put  a  living  sea-urchin  in  a  dish  of  sea-water  and  study  its 
movements. 

1.  When  placed  on  its  back,  how  does  it  turn  over? 

2.  What  is  the  normal  method  of  progression? 

3.  How  are  the  spines  arranged  when  the  animal  is  creeping 
on  the  bottom? 

4.  What  difference  do  you  note  between  the  spines  on  the 
lower  and  upper  surfaces? 

5.  How  long  are  the  tube  feet?    Are   they  used  with  the 
spines  in  moving  or  do  both  sets  of  organs  act  independently  ? 

6.  Grasp  a  spine  with  your  forceps  and  see  if  neighboring 
spines  respond.    Do  they  form  a  good  defensive  armor? 

7.  In  what  directions  may  a  spine  be  moved?    Remove  a 
spine  from  a  preserved  specimen  and  determine  how  it  was 
attached  and  how  the  muscles  that  moved  it  were  attached  to 
the  spine  and  to  the  test. 

Make  a  diagram  showing  the  arrangement. 

1  These  directions  will  serve  for  any  of  our  common  sea-urchins. 


STRONGYLOCENTROTUS.  69 

8.  Do  the  spines  have  any  definite  arrangement? 

9.  By  means  of  the  tube  feet,  notice  that  there  are  five  awfrw- 
lacral  areas,  between  which  are  five  inter-ambulacral  areas. 

10.  Notice  an  area  on  the  aboral  surface  which  is  free  from 
spines.     This  is  the  periproct. 

11.  Notice  the  membrane  around  the  mouth,  the  peristome. 

12.  Look  for  pedwellarice  on  the  peristome.     In  what  other 
places  are  pedicellariae  found?    Do  they  differ  from  those  of 
the  starfish? 

Draw  one.  »*• 

13.  Notice  the  tentacles  (modified  tube  feet)  on  the  peristome. 

14.  The  dermal  branchice  are  shrub-like  appendages  at  the 
outer  edge  of  the  peristome.    They  are  situated  opposite  each 
inter-ambulacral  area. 

Skeleton.1 — Examine  the  aboral  surface  of  a  cleaned  "test" 
and  note: 

1.  The  periproct  has  scattered  plates  which  cover  the  anal 
opening.     (Four  triangular  ones  in  Arbacia.) 

2.  Around  these  anal  plates  are  five  large  ones,  that  form 
the  apices  of  the  inter-ambulacral  series  of  plates.     These  are 
the  genital  plates,  and, each  is  perforated  by  a  small  opening, 
the  genital  pore. 

3.  That  one  of  the  genital  plates  is  larger  than  the  others 
and  is  full  of  very  minute  pores.     This  is  the  madreporite,  which 
is  homologous  with  the  madreporite  of  the  starfish.    Determine 
its  structure  with  a  lens. 

4.  Between  the  genital  plates  are  five  smaller  ocular  plates, 
also  perforated,  which  form  the  apices  of  the  ambulacral  series 
of  plates.    These  plates  and  the  genital  plates,  together  form, 
what  is  known  as  the  apical  system. 

5.  In  the  ambulacral  series  of  plates,  the  arrangement  of 
the  openings  (ambulacral  pores)  through  which  the  tube  feet 
protrude. 

1  If  a  preserved  specimen  of  Strongylocentrotus  be  placed  in  a  solution 
of  nitric  acid  (about  15  percent)  from  five  to  ten  minutes,  the  plates  of  the 
test  can  be  more  easily  seen,  especially  after  drying.  This  is  apparently 
due  to  the  coloring-matter  in  the  animal  itself.  Arbacia  is  not  helped  by 
the  treatment. 


70  ECHINODERMATA. 

6.  Do  all  of  the  plates  bear  balls  to  which  spines  were  artic- 
ulated?   Are  the  balls  of  equal  size?    Do  they  have  a  definite 
arrangement  ? 

Can  you  homologize  the  positions  of  the  ambulacral,  inter- 
ambulacral,  ocular,  and  genital  plates  in  the  sea-urchin  and 
starfish?  What  portion  of  the  starfish  is  represented  by  the 
periproct  of  the  sea-urchin? 

Make  a  drawing  of  the  test,  showing  the  ambulacral,  inter- 
ambulacral,  and  apical  systems  of  plates. 

7.  Around  the  peristome,  on  the  inside  of  the  test,  note  the 
five  auricles  forming  arches  or  bridges  over  the  bases  of  the 
ambulacral  areas.    Their  purpose  will  be  seen  later. 

With  a  scalpel  or  strong  scissors,  cut  around  the  equatorial 
region  of  an  alcoholic  specimen,  taking  care  to  cut  through  the 
test  only.  Break  or  cut  the  aboral  portion  away  bit  by  bit  until 
near  the  genital  plates,  freeing  the  fragments  from  the  internal 
organs  without  disturbing  their  positions. 

^  Reproductive  System. — How  were  the  gonads  (their  appear- 
ance is  the  same  in  both  sexes)  attached  to  the  test?  How 
many  are  there  ?  Opposite  what  areas  of  the  test  are  they  placed  ? 
Where  do  they  open  to  the  exterior?  Without  mutilating, 
find  the  narrow  strip  of  tissue  that  connects  the  gonads  to 
each  other  near  their  aboral  ends.  This  is  the  genital  rachis. 
Connected  with  the  genital  rachis  and  lying  alongside  the  stone 
canal,  which  leads  from  the  madreporite,  is  the  genital  stolon, 

-  Digestive  System. — Remove  the  gonads  from  the  three  areas 
farthest  from  the  madreporic  plate,  lift  the  remaining  aboral 
portion  of  the  test  slightly,  and  examine  the  alimentary  canal. 

1.  The  large  and  conspicuous  jaws,  frequently  called  the 
lantern.    They  will  be  studied  later. 

2.  The  esophagus,  passing  between  the  jaws,  and  bending 
over  to  one  side  to  join  the  intestine. 

3.  The  intestine.    Notice   its   size   and  its   shape.     Do   its 
loops  have  any  relation  to  the  positions  of  the  gonads? 

4.  The    intestinal    siphon,   lying    along    the    intestine    and 
attached  to  it  at  both  ends. 


STRONGYLOCENTROTUS.  71 

5.  The  rectum,  running  from  the  end  of  the  intestine  to  the 
anus. 

6.  The  mesenteries  which  hold  the  various  organs  in  place. 
Make  a  drawing  to  show  the  reproductive  and  digestive  organs. 

— ^  <*  Water-vascular  System. — 1.  The  stone  canal  leads  from  the 
(  madreporite  to  the  circular  canal,  which  encircles  the  esophagus 
V  at  a  point  just  above  the  lantern. 

2.  From  the  circular  canal  radial  tubes  pass  over  the  top  and 
down  the  sides  of  the  lantern,  to  pass  through  the  auricles  and 
up  the  ambulacral  tract,  to  the  ocular  plates.    They  can  be 
easily  seen  along  the  si<jjes  of  the  test,  but  are  difficult  to  see 
before  they  leave  the  lantern. 

3.  Along  the  course  of  each  radial  canal,  the  ampulla,  which 
supply  the  tube  feet,  are  to  be  seen.    The  relations  of  the  tube 
feet  and  radial  canals  are  practically  the  same  as  in  the  starfish 
except  that  the  removal  of  the  radial  tubes  to  the  inner  sides 
of  the  ambulacral  plates  causes  two  perforations  for  each  foot 
here,  while  the  starfish  has  only  one.     One  of  these  perforations 
is  for  the  connection  between  the  ampulla  and  the  foot,  the  other 
is  for  the  connecting  tube  between  the  radial  canal  and  the  foot. 
The  connecting  tube  joins  the  foot  outside  of  the  plate  (as  in 
the  starfish),  while  it  joins  the  radial  canal  inside  of  the  plates 
(different  from  the  starfish). 

Remove  the  intestine  and  study  the  lantern  and  its  attach- 
ments. 

1.  In  shape  the  lantern  is  a  five-sided  pyramid,  having  the 
"teeth"  at  its  apex  projecting  through  the  peristome.  The 
base  of  the  pyramid  may  be  compared  with  a  wheel,  in  which 
the  ten  epiphyses1  are  the  tire  and  the  five  radially  directed  rot- 
uloe  are  the  spokes,  each  one  of  which  has  a  more  slender  bar, 
forked  at  the  free  extremity,  the  compass  or  radius  lying  over  it. 
Each  of  the  five  segments  represents  a  jaw  that  is  articulated 
to  its  neighbors  at  its  base,  near  the  esophagus.  The  points 

1  In  Arbacia  the  epiphyses  form  small  hooks  that  do  not  unite  across 
the  base  of  an  alveolus. 


72  ECHINODERMATA. 

of  the  teeth  can  thus  be  separated  and  closed,  and  the  jaws 
protruded  and  retracted  by  means  of  muscles. 

2.  The  whole  lantern  is  inclosed  in  a  delicate  membrane, 
the  peripharyngeal  or  lantern  membrane  which  contains  the 
lantern  ccelom.    This  space  communicates  with  the  five  radial 
perihemal   canals,  which  run  along  the  ambulacral  areas  be- 
tween the  radial  canals  and  radial  nerves,  and  with  the  dermal 
branchse.     It  is  important  in  respiration. 

3.  Connecting  adjacent  alveoli  from  top  to  bottom  are  the 
comminator  muscles,  that  by  their  combined  action  close  the 
jaws. 

4.  To  each  of  the  arms  of  the  radius  fork  a  muscle  is 
attached.     Where  is  it  attached  at  the  other  end? 

5.  A  pair  of  protractor  muscles  pass  down  from  each  epi- 
physis.     To  what  are  they  attached?     They  are  used  in  pro- 
troding  the  jaws. 

6.  A  pair  of  retractor  muscles  is  attached  to  the  tip  of  each 
alveolus.     They  can  be  used  in  opening  the  jaws  or  in  retracting 
the  jaws.    Do  you  see  how? 

7.  There  are  also  internal  and  external  rotula  muscles  that 
connect  the  epiphyses  with   the  rotulse.     Their   contraction 
moves  these  plates  upon  one  another  and  thus  causes  a  rocking 
motion  of  the  jaws. 

Understand  how  the  jaws  may  be  protruded,  opened,  closed, 
and  retracted  by  means  of  these  muscles. 

8.  ^The  compasses  are  attached  one  to  the  other  by  the 
elevator  muscles.    Their  contraction  elevates  all  of  the  compasses 
and  thus  enlarges  the  lantern  ccelom. 

9.  Attached  to  the  forked  end  of  each  compass  is  a  pair  of 
depressor  muscles.    By  their  contraction  the  lantern  ccelom 
is  compressed. 

Understand  the  action  of  this  mechanism  in  respiration. 
(See  Cambridge  Natural  History,  Echinoderms,  p.  527.) 
Make  a  drawing  to  illustrate  the  arrangement  of  the  muscles. 

10.  Remove  the  lantern  by  cutting  the  peristome,  clear  away 
the  external  tissues,  and  examine  its  construction.     With  a 


STBONGYLOCENTROTUS.  73 

scalpel  cut  the  inter-alveolar  muscles  so  the  jaws  may  be  sepa- 
rated. Find: 

(a)  The  large  V-shaped  alveoli  (a  straight  suture  indicates 
that  each  is  formed  by  the  fusion  of  two  parts).  Notice  the 
roughenings  on  their  esophageal  sides.  What  purpose  can  they 
serve  ?  Why  should  the  alveoli  be  so  large  and  the  inter-alveolar 
muscles  so  strong? 

(6)  The  epiphyses,  which  are  fused  with  the  upper  corners  of 
each  alveolus  and  extend  in  to  form  a  bar  over  its  base,  thus 
being  functionally  a  part  of  the  alveolus  itself.  The  sutures  be- 
tween them  and  the  alveolus  proper  can  usually  be  seen. 

(c)  The  rotulce,  one  of  which  joins  the  ends  of  each  epi- 
physis  and  extends  to  the  position  of  the  esophagus.     The  five 
rotulas  of  the  lantern  articulate  with  each  other  around  the  eso- 
phagus, and  each  rotula  articulates  with  the  epiphyses  of  two 
adjacent  jaws.    Do  you  understand  how  the  jaws  move  on  the 
rotulse? 

(d)  The  compasses,  lying  over  the  rotulse,  are  slender  and 
bifurcated  at  their  outer  ends. 

(e)  Inclosed  in  each  alveolus  is  a  tooth.      Examine  both 
extremities  of  it  and  determine  why  the  inner  end  is  soft. 

Understand  thoroughly  how  the  jaws  are  used  and  why  the 
animal  needs  them.  Why  does  the  sea-urchin  not  need  large 
hepatic  caeca? 

The  Nervous  System. — The  nervous  system  is  difficult  to 
demonstrate  in  dissections,  but  is  easy  to  trace  in  sections.  It 
consists  of: 

1.  A  nerve  ring  that  encircles  the  esophagus  at  a  point  just 
above  the  mouth. 

2.  Five  radial  nerves  that  pass  from  the  ring,  along  the  in- 
side of  the  ambulacral  areas  of  the  test,  to  the  ocular  plates. 

The  radial  water  tubes  will  be  found  in  sections  adjacent 
to  the  radial  nerves.  The  two  are  separated  only  by  a  narrow 
space,  the  pseudohsemal  canal.  Between  the  radial  nerves 
and  the  tissue  of  the  test  there  is  another  narrow  cavity,  the 
epineural  sinus. 


74  ECHINODERMATA. 

If  time  permits,  students  will  find  a  dissection  of  the  sand- 
dollar,  Echinarachnius,  valuable  for  purposes  of  comparison. 
Special  notes  will  not  be  necessary.  Its  shape  and  restricted 
ambulacral  areas  should  be  studied  in  the  light  of  its  habits 
and  food-supply.  How  does  the  animal  move  ? 

MacBride:  Cambridge  Natural  History,  Echinodermata. 

Von  Uexhull:  Die  Physiologic  des  Seeigelstachels.     Zeit.  f.  Biol.,  39. 

:  Ueber  die  Function  der  Polischen  Blasen  am  Kauapparat  der  regu- 

laren  Seeigel.     Mitth.  Zool.  Stat.  Neapel.,  12,  1897. 


HOLOTHUROIDEA. 

THYONE.     (Sea-Cucumber.) 

These  animals  may  be  found  in  protected  and  usually  muddy 
places,  concealed  in  eel-grass.  They  are  generally  so  effectually 
concealed  that  they  cannot  be  satisfactorily  studied  in  their 
native  places.  It  is  desirable  to  visit  places  where  they  occur 
and  find  specimens  by  feeling  for  them  near  the  bottom.  It 
is  then  possible  to  realize  the  life  for  which  they  are  adapted. 

Examine  living  expanded  specimens  in  an  aquarium  (taking 
care  not  to  disturb  them)  and  note : 

1.  How  the   tentacles  are  used.     What  kind  of  food  would 
it  get  by  this  means?    Compare  the   method  of  food-getting 
with  the  starfish  and  sea-urchin. 

2.  The   respiratory   movements  of  the   body.    Notice   the 
strength  of  the  current  of  water  ejected. 

3.  The  general  shape  of  the  body  when  expanded.     Does 
it  seem  to  rest  on  a  particular  side  ? 

4.  The  number  and  arrangement  of  the  tentacles.     To  what 
do  they  probably  correspond  in  the  sea-urchin? 

Kill  the  specimen  by  catching  it  with  strong  forceps  behind 
the  mouth,  when  the  tentacles  are  expanded,  and  holding  it  in 
hot  water.  Note  that : 

1.  The  body  is  covered  with  papilliform  ambulacral  feet. 
It  is  possible  in  some  cases  to  see  that  they  are  arranged  in  five 
broad,  longitudinal  bands. 


THYONE.  75 

2.  The  suckers  are  less  abundant  on   the  dorsal   (upper) 
surface  than  on  the  ventral. 

3.  A  small  papilla  is  to  be  found  on  the  dorsal  surface,  be- 
tween the  tentacles.     On  it  is  the  gemtal^^enj^Q.    This  will  be 
referred  to  again. 

Make  a  drawing  of  the  animal  as  seen  from  the  side,  indicat- 
ing all  of  the  points  of  structure  that  have  been  seen. 

With  a  pair  of  scissors,  open  the  animal  longitudinally  along 
the  middle  of  the  ventral  (lower)  surface. 

Digestive  System. — 1.  Note  the  delicate  perforated  mesen- 
tery, which  attaches  it  to  the  walls  of  the  body. 

2.  The  esophagus,    leading    from    the   mouth    through    a 
calcareous  structure,  which  recalls  the  lantern  of  the  sea-urchin. 
Examine  and  see  if  the  arrangement  is  similar  to  that  of  the 
sea-urchin  lantern.     The  muscles  for  the  retraction  of  the 
lantern  are  frequently  torn  from  their  attachments  at  one  end. 

3.  The  thin-walled  and  enlarged  stomach. 

4.  The  coiled  intestine,  which  leads  to  the  cloaca. 
Draw  the  alimentary  canal  in  position. 

Cut  the  alimentary  canal  just  in  front  of  the  stomach,  and 
close  to  the  cloaca,  and  as  you  remove  it  notice  the  blood-vessel 
that  runs  along  the  intestine. 

Respiratory  and  Excretory  System. — Arising  laterally  from 
either  side  of  the  cloaca  are  the  two  respiratory  trees.  They  are 
branched  and  project  far  forward  into  the  body-cavity.  Can  you 
determine  how  they  are  filled  with  water  and  how  the  water  is  ex- 
pelled? With  a  pipet  inject  them  with  starch-mass.  The  strong 
jets  of  water  ejected  by  the  living  specimen  were  thrown  from 
these  tubes.  Can  you  understand  how  they  serve  for  respira- 
tion? The  walls  of  the  tubes  composing  the  trees  are  glandular 
and  may  thus  serve  to  excrete  wastes.  Notice  the  muscles  that 
radiate  from  the  walls  of  the  cloaca  to  the  body-wall.  What 
is  their  function? 

Make  a  drawing  of  the  cloaca  and  rspiratory  trees. 

Reproductive  System. — The  single  gonad  (ovary  or  testis) 
occupies  a  median  dorsal  position  in  the  anterior  part  of  the 


76  ECHINODEEMATA. 

body-cavity.  It  is  composed  of  a  multitude  of  filaments,  which 
join  to  make  a  brush.  This  brush  projects  backward  into  the 
body-cavity.  The  duct  of  the  organ  lies  along  the  dorsal  mid- 
line,  between  the  right  and  left  dorsal  muscle  bands,  and  leads 
to  the  opening  upon  the  small  papilla  near  the  mouth  that  has 
already  been  noticed. 

Water-vascular  System. — 1.  The  circular  canal  can  be  found 
in  favorable  specimens,  surrounding  the  deeper  portions  of  the 
esophagus.  It  gives  rise  to  one  or  two  Polian  vesicles,  which 
are  very  large  and  hang  down  into  the  body-cavity. 

2.  The  five  radial  canals  (homologous  with  the  radial  canals 
of  the  starfish  and  sea-urchin)  originate  from  the  water-ring, 
pass  forward  and  then  backward,  and  end  near  the  cloaca.     The 
course  of  each  radial  canal  is  easily  followed  by  means  of  the 
numerous  small,  elongated  ampullae  which  supply  the  tube  feet. 

3.  Ten   forwardly   directed   canals,    the   tentacular   canals, 
leave  the  radial  canals  near  the  water-ring  and  pass  into  the 
tentacles,  which  may  be  homologized  with  tube  feet. 

4.  The  stone  canal  and  madreporite  are  much  reduced  in 
holothurians.      The  madreporite,  except  in  larvae  and   very 
young   specimens,   is  not  found  on  the  outer   surface.     The 
stone  canal  leads  obliquely  backward  from  the  water-ring, 
toward  the  dorsal  body-wall,  to  join  a  small  calcareous  body,  the 
madreporite,  which  lies  in  the  body-cavity  and  is  not  perfor- 
ated.    Does  this  give  you  a  reason  for  the  presence  of  large 
Polian  vesicles?    The  liquid  in  the  water-vascular  system  is 
not  sea-water.     Notice  its  color. 

Make  a  diagram  of  the  water-vascular  system. 

Muscular  System. — Beside  the  special  muscles  radiating 
from  the  cloaca  which  have  been  referred  to  in  connection  with 
the  respiratory  system,  and  the  muscles  of  the  lantern,  there  are 
five  strong  longitudinal  bands,  really  pairs.  In  which  areas 
do  they  lie?  What  function  do  they  perform?  Look  for  smaller 
circular  bands.  Are  there  many  of  them?  What  is  their 
function?  Can  you  explain  the  varied  worm-like  motions  of 
the  body  by  the  action  of  these  muscles? 


THYONE.  77 

Nervous  System. — This  cannot  be  satisfactorily  studied  in 
dissections.  There  are  five  radial  nerves  and  a  circular  ring. 
The  cords  are  embedded  in  the  body-wall  and  are  hard  to  find. 

The  classes  of  the  Echinodermata  show  exceptionally  well 
how  a  general  type  of  structure  may  be  retained  and  still  modi- 
fied in  certain  regards  for  special  habits.  Compare,  for  instance, 
the  feeding  habits  of  the  starfish,  sea-urchin,  and  sea-cucumber. 


ANNELIDA* 

Body  elongated,   generally   divided   into   somites.    Coelom 
usually  extensive.    Appendages  when  present  form  parapodia. 

CLASS  1.  Archi-annelida. 

Without  setae  or  parapodia.    Nervous  system  not 
separate  from  the  epidermis.     (Polygordius. ) 
CLASS  2.  Chaetopoda. 

With  numerous,  distinct  somites  that  are  pro- 
vided with  setse. 
Subclass  1.  Archi-chaetopoda. 

Setae  retractile.    Nervous  system  not  separate 
from  the  epidermis.     (Saccocirrus.) 
Subclass  2.  Polychaeta. 

With  numerous  setae.  With  a  great  variety  of 
structure.  (Nereis,  Autolytus,  Lepidonotus, 
Diapatra,  Chaetopterus,  Cistenides,  Spirorbis, 
Clymenella,  Sabella,  Hydroides,  Arenicola,  Am- 
phitrite.) 
Subclass  3.  Myzostomida. 

Disk-shaped.     Without   external   segmentation. 
Parasites  on  Echinodermata.     (Myzostoma.) 
Subclass  4.  Oligochaeta. 

Without    parapodia.     Setae    few    and    simple. 
(Tubifex,  Lumbricus.) 
CLASS  3.  Gephyrea. 

No  segmentation.     With  or  without  setae.     With 
•  introvert  or  proboscis. 
Order  1.  Inermia. 

With  introvert.    Anus  dorsal.     No  setae.    (Phas- 
colosoma.) 
Order  2.  Armata. 

With    proboscis.    Anus    posterior.    Setae    few. 
(Echiurus.) 
CLASS  4.  Hirudinea. 

Somites  constant  in  number,  with  more  external 
annuli  than  there  are  somites.     With  sucking 
mouth  and  posterior  sucker. 
78 


NEREIS  VIRENS.  79 

Order  1.  Rhynchobdellida. 

Anterior  end  of  body  forming  a  proboscis  or  in- 
trovert. No  jaws.  (Glossiphonia,  Pontob- 
della,  Clepsine.) 

Order  2.  Gnathobdellida. 

No  proboscis  or  introvert.  Mouth  usually  with 
three  teeth.  (Hirudo.) 

Hatschek:   Studien  iiber  Entwicklungsgeschichte  der  Anneliden.     Arb. 

Zool.  Inst.  Wien,  1,  1878. 
Norman:  Diirfen  wir  aus  den  Reactionen  neiderer  Thiere  auf  des  Vorhan- 

densein  von  Schmerzempfindungen  Schliessen?    Arch.  ges.  Physiol.,  67, 

1897. 


CHJETOPODA. 

NEREIS  VIRENS.    (dam-Worm.) 

These  animals  may  be  found  inhabiting  mud-flats  from  which 
the  water  flows  at  low  tide.  Occasionally  they  may  be  seen  with 
their  head  ends  protruding  from  their  burrows,  but  generally 
specimens  will  have  to  be  dug.  Notice  the  conditions  under 
which  the  animals  live  and  the  forms  with  which  they  are  asso- 
ciated. It  should  also  be  understood  that  many  of  their  worst 
enemies  are  present  only  when  the  water  covers  their  burrows. 

External  Structure. — 1.  Examine  a  living  worm  in  a  dish 
of  sea-water,  noting  the  motions  of  the  body  and  of  the  parapodia 
or  swimming  feet. 

Make  a  drawing  of  the  animal. 

2.  Hold  it  down  against  the  bottom  of  the  dish  or  place  in 
fresh  water  for  a  few  minutes  to  induce  it  to  protrude  the 
proboscis,  the  protrusible  anterior  portion  of  the  alimentary 
canal.     This  is  lined  with  chitin  and  armed  with  numerous 
denticles  and  a  pair  of  lateral  jaws. 

3.  Is  the  general  surface  clean  or  slimy?    Compare  with  the 
earthworm  in  this  respect  and  explain  the  basis  for  the  difference. 

4.  Determine  the  direction  of  the  peristaltic  waves  in  the 
dorsal  blood-vessel. 

5.  Is  the  median  ventral  nerve  cord  visible  through  the  body- 
wall? 


80  ANNELIDA. 

6.  In  a  freshly  killed  or  preserved  worm,  count  the  segments  or 
metameres  and   compare  it  with  your  neighbor's  to  ascertain 
whether  the  number  is  constant.     What  segments,  if  any,  are 
devoid  of  parapodia  ?    Why  ? 

7.  In  the  head  distinguish  the  prostomium,  which  bears  the 
four  eyes  and  a  pair  of  short  terminal  tentacles.    At  each  side  of  the 
prostomium  is  a  thick  palp.    Determine  whether  the  worm  has 
the  sense  of  vision,  and  whether  its  sense  of  touch  is  delicate. 

8.  Also  in  the  head  find  the  peristomium,  the  segment  which 
surrounds  the  mouth  and  bears  four  pairs  of  lateral  tentacles  or 
cirri.    Stretch  the  mouth  with  forceps. 

Make  an  enlarged  drawing  of  the  head. 

9.  Find  the  small  terminal  anus  and  a  pair  of  caudal  cirri  on 
the  last  segment. 

10.  With  scissors  cut  off  a  parapodium  close  to  the  body  and 
observe  that  it  has  a  dorsal  blade  and  a  ventral  blade  (notopodium 
and  neuropodium).     Each  of  these  contains  a  bundle  of  bristles 
or  setce.    What  use  can  you  ascribe  to  the  setae  ?    In  each  bundle 
is  one  very  thick  seta,  the  aciculum,  which  extends  into  the  body 
and  is  attached  to  muscles.     Of  what  use  is  the  aciculum?    Ex- 
amine a  few  of  the  small  setae  microscopically.     What  is  their 
structure?    Why  is  it  desirable  to  have  so  many  of  the  small 
setae?    Why  does  this  animal  need  more  than  an  earthworm 
needs? 

Observe  that  each  parapodium  has  a  small  dorsal  and  a  small 
ventral  cirrus,  and  that  the  main  portion  of  both  notopodium 
and  neuropodium  has  the  form  of  a  flattened  blade,  somewhat 
divided  into  lobes.  The  largest  lobe  of  the  notopodium  is  very 
thin  and  vascular.  What  function  can  you  ascribe  to  it? 

Draw  a  parapodium. 

11.  Look  for  the  nephridiopores,  minute  apertures  which  are 
segmentally  placed  on  the  ventral  surface  near  the  neuropodial 
cirri. 

Internal  Structure. — For  dissection  use  a  specimen  that  has 
been  killed  and  fasten  it  down  by  a  pin  through  the  head  and  one 
through  the  posterior  part.  With  scissors  cut  throu  ^h  the  body- 
wall,  longitudinally,  near  the  mid-dorsal  line. 


NEREIS   VIRENS.  81 

Find  the  dissepiments  which  divide  the  ccelom,  or  body-cavity, 
into  metameric  chambers.  Cut  through  the  dissepiments  with 
scissors  and  pin  the  edges  of  the  body-wall  apart,  progressing 
toward  the  head. 

Circulatory  System. — The  dorsal  blood-vessel  lies  along  the 
dorsal  surface  of  the  alimentary  canal  and  gives  off  branches  in 
each  segment,  which  ramify  through  the  body-wall  and  viscera 
and  connect  with  the  longitudinal,  ventral  blood-vessel.  The 
blood-plasma  contains  red  coloring-matter  in  solution. 

Digestive  System. — The  mouth-cavity  leads  into  a  muscu- 
lar pharynx,  a  portion  of  which  is  protrusible  as  the  proboscis. 
Examine  carefully  the  muscles  of  the  pharynx,  protractors  and 
retractors,  and  ascertain  their  attachments.  Posterior  to  the 
pharynx  find  a  small  dilation  and  a  narrow  esophagus  with 
a  digestive  gland  at  each  side.  Where  does  the  duct  of  the 
gland  open?  In  the  very  long  stomach-intestine,  which  follows  the 
crop,  note  the  constrictions  and  their  relations  to  the  dissepi- 
ments. Can  you  demonstrate  dorsal  or  ventral  mesenteries? 
Cut  open  the  pharynx  and  the  anterior  end  of  the  stomach- 
intestine  and  note  the  character  of  their  walls. 

Make  a  drawing  of  the  digestive  system. 

Muscular  System. — How  many  distinct  bands  of  longitu- 
dinal  muscles  can  be  distinguished?  Examine  with  a  hand-lens 
the  parapodial  muscles  attached  to  the  base  of  the  acicula.  Can 
you  make  out  a  layer  of  circular  muscles?  Of  what  layers  does 
the  body-wall  consist? 

Excretory  System. — The  nephridia  are  not  nearly  as  easily 
found  or  studied  as  they  are  in  the  earthworm.  Near  or  just 
beneath  the  lateral  edges  of  the  ventral  muscle-bands  find  the 
minute  pear-shaped  nephridia.  Determine  their  distribution 
in  the  body.  Each  nephridium  consists  of  a  tortuous  canal  in 
a  multi-nucleate  mass  of  protoplasm.  The  external  opening  is 
the  nephridiopore  above  mentioned.  The  inner  end  perforates 
the  dissepiment  anterior  to  the  body  of  the  nephridium  and 
opens  into  the  coelomic  cavity  of  the  segment  next  in  front, 
by  a  ciliated  funnel,  the  nephrostome.  With  a  hand-lens  try  to 
6 


82  ANNELIDA. 

find  the  nephrostome.  Remove  a  nephridium  by  means  of  fine 
forceps  and  examine  it  with  a  microscope. 

Reproductive  System. — The  sexes  are  separate,  but  no  per- 
manent gonads  are  present.  At  the  breeding  season  the  ova 
or  spermatozoa  are  proliferated  from  the  coslomic  epithelium 
of  a  large  number  of  segments  and  escape  by  rupture  of  the 
body-wall. 

Nervous  System.1 — On  lifting  the  alimentary  canal  you  will 
see  the  ventral  ganglionated  nerve  cord.  Note  the  nerves  pass- 
ing off  laterally  from  the  ganglia.  How  many  pairs  of  nerves 
per  segment  are  there,  and  how  are  they  placed?  Are  the  gan- 
glia metameric?  Is  there  any  indication  that  the  nerve  cord  is 
double?  At  the  anterior  extremity  of  the  cord  note  the  infra- 
esophageal  ganglia  and,  extending  from  them  and  encircling  the 
anterior  end  of  the  alimentary  canal,  the  circum-esophageal  con- 
nectives which  unite  above  in  the  bilobed  brain  or  supra-eso- 
phageal  ganglia.  Sensory  nerves  connect  the  brain  with  the  eyes, 
tentacles,  and  palps. 

Make  a  drawing  of  the  nervous  system. 

Lillie:  Studies  of  Fertilization  in  Nereis.    I  and  II.  Jour.  Morph.,  22, 1911. 

III.  and  IV.  Jour.  Exp.  Zpol.,  12,  1912. 
Mayer:  The  Annual  Breeding-swarm  of  the  Atlantic  Palolo.     Carnegie 

Inst.  Pub.,  102,  1908. 
E.  B.  Wilson:  The  Cell-Lineage  of  Nereis.  A  Contribution  to  the  Cytology 

of  the  Annelid  Body.     Jour.  Morph.,  6,  1902. 
Woodworth:  The  Palolo  Worm,  Eunice  viridis.     Bui.  Mus.  Comp.  Zool., 

Harvard,  51,  1907. 

LUMBRICUS.    (Earthworm.) 

Earthworms  feed  mostly  at  night.  What  reason  is  there 
for  this  habit?  You  should  look  for  earthworms  with  a  lantern 
some  mild,  calm  summer  evening  when  the  ground  is  quite 
moist.  See  if  they  leave  their  burrows  entirely.  How  much 

1  The  nervous  system  can  be  most  readily  studied  by  tearing  it  out  with 
needles  in  a  specimen  which  has  been  macerated  in  20  percent  nitric  acid 
for  twenty-four  hours.  Sensory  cells  and  their  neurites  can  be  identified 
in  the  parapodia  by  placing  them  in  a  1  percent  solution  of  ammonium 

Eicrate  after  having  let  vigorous  worms  crawl  around  for  three  or  four 
ours  in  a  small  amount  of  1  percent  solution  of  methylen-blue.     Mounts 
of  the  parapodia  should  be  made  in  a  mixture  of  glycerin  and  ammonium 
picrate  solution. 


LTJMBRICTJS.  83 

of  the  body  is  generally  protruded?  Can  you  determine  what 
the  worms  are  doing?  Are  they  disturbed  by  walking  near 
them?  Are  they  ever  disturbed  by  flashing  the  light  suddenly 
upon  them?  Of  what  service  to  them  is  the  ability  to  distin- 
guish light  ?  Look  for  castings  near  the  burrows.  During  day- 
light look  for  castings  and  thus  determine  the  relative  abundance 
of  worms  in  lawns,  gardens,  etc.  (As  the  worms  come  to  the 
surface  only  when  it  is  moist,  castings  will  be  abundant  only 
at  such  times.)  Do  the  castings  indicate  anything  about  the 
feeding  habits. 

Place  a  living  specimen  upon  moist  filter-paper  and  observe 
the  direction  and  method  of  movement.  How  can  it  reverse  its 
direction?  Gently  touch  different  parts  of  the  body  to  see 
which  are  the  most  sensitive. 

Observe  the  movement  of  the  blood  in  the  dorsal  vessel.  In 
what  direction  does  it  move?  Does  the  vessel  change  in  shape? 

Place  a  preserved  specimen  in  a  dish  with  a  little  water  and 
notice: 

1.  The  difference  in  shape  of  the  two  ends  of  the  body.    The 
mouth  is  at  the  anterior  end,  below  the  protruding  lobe  of  the 
prostomium.     The  anus  is  a  vertical  slit  at  the  end  of  the  last 
somite. 

2.  The  dorsal  and  ventral  sides.     How  do  they  differ? 

3.  The  right  and  left  sides  are  symmetrical.    Count  the  somites 
of  the  body,  compare  with  others,  and  record  the  result. 

4.  On  the  anterior  third  of  the  body  certain  somites  are 
swollen  and  form  the  clitellum.     What  somites  are  swollen? 
The  clitellum  is  not  present  in  young  individuals.     It  is  used  in 
making  egg-cases  and  providing  food  for  developing  embryos. 
Understand  how  this  is  accomplished. 

5.  Small  swollen  areas  on  the  ventral  side  of  the  fifteenth 
somite,  where  the  vasa  defer entia  open. 

6.  Setce  project  slightly  from  the  surface  of  each  somite. 
These  light  colored  spines  are  easily  felt  with  the  fingers.     See 
if  you  can  determine  the  number  and  position  of  the  rows  by 
stroking  gently.    How  are  they  used  ? 


84  ANNELIDA. 

Draw  a  ventral  view  of  the  anterior  end,  including  the  clitellum, 
and  another  view  of  the  posterior  end. 

Taking  care  not  to  cut  deep,  with  fine  scissors  cut  through 
the  dorsal  wall  of  the  body,  and  extend  the  cut  the  whole  length 
of  the  body.  Carefully  spread  and  pin  the  animal  open.  In 
doing  this  you  must  tear  or  cut  the  septa,  but  be  careful  not  to 
tear  or  break  the  organs  that  perforate  them. 

Alimentary  Canal. — This  consists  of  a  straight  tube  that 
runs  the  length  of  the  body. 

1.  Immediately  behind  the  mouth  is  a  muscular,  white  organ, 
the  pharynx.    Through  how  many  somites  does  this  extend  ?    It  is 
connected  with  the  body-wall  by  numerous,  radiating  muscle 
fibers.    What  function  do  these  fibers  perform? 

2.  Behind  the  pharynx  is  the  narrow  and  long  esophagus. 
This  runs  posteriorly  between  lobed,  light  colored  organs,  the 
seminal  vesicles,  that  will  be  studied  in  connection  with  the 
reproductive  organs.    Press  these  aside  and  notice  the  small 
cakiferous  glands. 

3.  The  esophagus  leads  to  the  crop,  which  lies  just  anterior 
to   and   in   contact   with  the   gizzard.     In  what    somites   are 
these  organs  placed?    What  is  their  shape ?    Do  you  understand 
the  function  of  each? 

4.  Leaving  the  gizzard  is  the  stomach-intestine,  which  runs 
through  the  remainder  of  the  body,  giving  off  lateral  diverticula 
in  each  somite.     Do  you  know  its  function? 

Notice  the  relation  of  the  septa  to  the  alimentary  canal. 

Circulatory  System.  —  1.  Lying  dorsal  to  the  alimentary 
canal  is  the  blood-vessel  that  could  be  seen  pulsating  in  the 
living  specimen.  In  most  cases  this  vessel  is  full  of  blood  and 
appears  brown. 

2.  Near  the  anterior  end  of  the  body  large  side  branches, 
the  aortic  arches,  are  given  off  on  either  side  and  pass  down 
around  the  esophagus.     How  many  aortic  arches  do  you  find? 
In  what  somites  are  they  placed  ? 

3.  Examine  with  a  lens  and  see  whether  you  find  other  vessels 


LUMBRICTJS.  85 

connected  with  the  dorsal  aorta.  If  you  do  determine,  how  are 
they  placed?  Do  they  appear  like  the  aortic  arches? 

Make  a  drawing  of  the  anterior  end  of  the  body,  showing  the 
points  you  have  seen. 

4.  Gently  press  the  stomach-intestine  to  one  side  and  see  if 
you  find  a  blood-vessel  beneath  it.  Do  the  aortic  arches  join 
this?  Other  connections  between  blood-vessels  are  too  small  to 
be  studied  in  dissections,  but  you  should  understand  from  text- 
books or  lectures  what  they  are,  and  the  probable  course  of  cir- 
culation. 

Excretory  System. — 1.  A  pair  of  nephridia  occurs  in  each 
somite,  one  nephridium  on  either  side  of  the  alimentary  canal. 
(The  first  three  or  four  somites  are  not  provided  with  nephridia.) 
Each  nephridium  is  a  coiled  tube,  appearing  to  the  unaided 
eye  as  a  fluffy  mass,  that  opens  externally  between  the  groups 
of  setae,  in  the  position  already  observed,  and  internally  by  a 
small  opening,  the  funnel.  The  inner  opening  is  not  in  the 
somite  in  which  the  most  of  the  tube  lies,  but  in  the  somite 
anterior  to  it.  That  is,  the  nephridium  that  occupies  the  space 
in  somite  twenty,  opens  externally  on  somite  twenty,  but  in- 
ternally perforates  the  septum  directly  anterior  and  opens  into 
somite  nineteen. 

2.  Remove  a  nephridium  with  your  forceps  and  examine  it 
with  your  microscope.  Notice  that  it  consists  of  a  coiled  tube 
of  varying  diameter.  The  funnel  is  not  easy  to  find  and  is  hard 
to  remove.  It  may  be  found  by  removing  the  portion  of  the 
septum  through  which  the  nephridium  passes  and  examining 
it  with  a  microscope. 

Draw  the  nephridia  into  your  previous  figure. 

Cut  the  stomach-intestine  behind  the  gizzard  and  pull  it 
forward,  carefully  separating  the  tissue  from  it  as  it  is  drawn  for- 
ward, so  underlying  organs  will  not  be  disturbed.  In  this  way 
free  the  alimentary  canal  to  the  position  of  the  pharynx. 

You  can  now  see  the  extent  of  the  nephridia,  and  possibly 
see  where  they  perforate  the  septa. 


86  ANNELIDA. 

Reproductive  System. — 1.  The  seminal  vesicles  are  large 
white  bodies,  united  in  the  median  line. '  They  send  three  lobes 
on  either  side,  that  normally  overlap  the  posterior  part  of  the 
esophagus.  In  what  somites  do  the  lobes  occur? 

2.  Carefully  open  the  seminal  vesicles  near  the  median  dor- 
sal line  and  examine  their  contents  microscopically. 

3.  With  a  pipet  wash  out  the  contents  and  notice  the  two 
pairs  of  convoluted  funnels,  the  inner  openings  of  the  vasa  defe- 
rentia.    The  testes  are  hard  to  find,  as  they  are  the  same  color 
as  the  coagulated  mass  that  filled  the  seminal  vesicles.     Thev 
are  attached  to  the  septa  just  anterior  to  the  funnels.    The 
narrow  tubes  of  the  vasa  deferentia  may  sometimes  be  seen  leav- 
ing the  seminal  vesicles.    They  open  externally  on  somite  fifteen. 

4.  The  ovaries  are  a  pair  of  very  small  organs  attached  to  the 
posterior  surface  of  the  septum  that  separates  the  twelfth  from 
the  thirteenth  somite,  near  the  mid-ventral  line.    They  may 
sometimes  be  found  with  a  lens,  but  are  not  usually  visible  other- 
wise.    If  possible,  remove  an  ovary  and  examine  it  with  a  micro- 
scope to  see  its  shape,  and  to  find  which  portion  has  the  most 
mature  eggs.    The  oviducts  open  into  the  cavity  of  the  thirteenth 
somite  and  externally  through  the  ventral  wall  of  the  fourteenth 
somite,  in  line  with  the  nephridia.    They  can  seldom  be  seen  in 
dissections. 

5.  Between  the  ninth  and  tenth  and  the  tenth  and  eleventh 
somites,  on  the  ventral  side,  are  two  pairs  of  white,  rounded 
pouches,  the  seminal  receptacles,  that  open  externally  but  not 
internally.     Understand  their  function.     Make  a  drawing  of 
the  reproductive  system. 

Nervous  System. — 1.  On  the  dorsal  surface  of  the  pharynx, 
near  its  anterior  end,  are  the  two  cerebral  ganglia.  They  lie  on 
either  side  of  the  median  line  and  are  connected  by  a  stout  com- 
missure. In  what  somite  do  they  lie  ? 

2.  The  remainder  of  the  ganglia  lie  ventral  to  the  alimentary 
canal.  The  first  ventral  ganglia  are  connected  with  the  cerebral 
ganglia  by  connectives  that  pass  around  the  sides  of  the  pharynx. 
Adjacent  ganglia  of  the  ventral  chain  are  united  by  connec- 


LUMBRICTJS.  87 

lives.  The  ganglia  of  each  somite,  and  the  cords  that  connect 
those  of  adjacent  somites,  are  fused  so  that  the  original  paired 
condition  is  not  very  apparent.  How  far  does  the  ventral  chain 
of  ganglia  extend?  Where  do  nerves  leave  it? 

Draw  the  nervous  system  into  the  figure  that  shows  the  repro- 
ductive system. 

Notice  the  sacs  that  inclose  the  setae  and  indicate  them  in 
the  above  figure. 

Examine  prepared  serial  microscopic  sections.1 

1.  The  cuticle  will  probably  be  absent  in  most  sections,  in 
which  case  the  outer  covering  will  be  the  cellular  hypodermis  or 
skin.     How  many  cells  thick  is  this  layer?    Look  for  the  gland 
cells  that  keep  the  living  worm  moist.     Do  you  know  how  the 
cuticle  is  formed? 

2.  Beneath  the  hypodermis  is  the  circular  muscle  layer,  which 
is  followed  by  the  longitudinal  muscle  layer.     The  fibers  of  the 
latter  are  arranged  in  conspicuous  bundles.     Lining  the  body- 
wall  is  the  thin  peritoneal  layer.     Do  you  understand  the  func- 
tion of  each  of  these  layers?     How  is  the  body  elongated? 

3.  Find  the  setce  and  determine  where  they  are  placed,  how 
many  are  in  each  group,  how  many  groups  there  are,  how  they 
pierce  the  body-wall,  and  what  muscles  are  attached  to  them. 
Why  are  setae  not  in  every  section? 

4.  The   alimentary   canal    consists   of   a   lining  epithelium, 
followed  by  connective  tissue  and  muscle,  and,  on  its  outer  wall, 
peritoneal  cells,  which  in  the  region  of  the  stomach-intestine 
are  large,  very  numerous,  and  are  known  as  the  chloragog  cells. 

5.  Lying  in  the  mid-ventral  line,  beneath  the  alimentary 
canal   and   close   to   the   body-wall,  is  the  ventral  nerve  cord. 
Examine  its  structure.     See  if  any  of  the  sections  show  nerves 
leaving  it. 

1  Small  worms  should  be  kept  in  a  dish  and  fed  on  clean  moistened 
filter-paper,  which  they  will  eat  readily,  until  the  alimentary  canal  is  free 
from  grit,  before  they  are  preserved  for  sectioning.  It  is  well  to  narcotize 
them  by  placing  them  in  a  small  quantity  of  water  and  adding  a  little 
alcohol  from  time  to  time  (never  enough  to  make  the  worms  squirm  vio- 
lently) until  they  cease  to  move.  They  may  then  be  killed  with  subli- 
mate acetic  or  other  killing  agent  and  treated  in  the  usual  manner. 


88  ANNELIDA. 

6.  Dorsal  to  the  alimentary  canal  is  the  dorsal  blood-vessel,  on 
its  ventral  side  is  the  ventral  blood-vessel,  and  ventral  to  the  nerve 
cord  the  sub-neural  vessel. 

7.  Find  sections  of  the  nephridia.     Where  are  they  placed? 
How  do  the  sections  appear?    Why? 

Other  organs  will  appear  in  most  of  the  sections.  See  if  you 
can  identify  them. 

Draw  an  enlarged  cross-section. 

Parker  and  Arkin:  The  Directive  Influence  of  Light  on  the  Earthworm, 

Allolobophora  foetida.     Am.  Jour.  Physiol.j  4,  1901. 
Sedgewick  and  Wilson:  General  Biology. 

AUTOLYTUS  CORNUTUS. 

This  polychaete  lives  in  cylindrical  tubes  of  its  own  con- 
struction that  it  attaches  to  seaweeds  and  hydroids,  and  is  espe- 
cially interesting  because  of  its  method  of  reproduction,  by  bud- 
ding. 

Study  live  and  preserved  specimens  with  the  naked  eye  and 
with  the  hand-lens,  in  order  to  form  a  correct  idea  of  its  natural 
color,  size,  and  movements,  and  then  study  stained  specimens 
with  the  low  power. 

1.  Observe  two  individuals  attached  end  to  end.     The  ante- 
rior one  is  a  non-sexual  zooid  (or  original  "stock")  and  is  giving 
rise  to  a  new  sexual  zooid  by  budding.     Counting  the  peristomium 
as  one  somite,  on  what  somite  does  the  bud  begin  and  what 
does  it  represent? 

2.  Study  the  head  of  the  anterior,  non-sexual  zooid.  Find  three 
prostomial  tentacles.     How  are  they  arranged?     Find  the  eyes. 
How  many  pairs  are  there?    Do  you  find  palps?     On  the  peri- 
stomium find  the  two  tentacles  and  a  tentacular  cirrus. 

3.  On  the  succeeding  somites  study  the  parapodia.     Observe 
the  large  dorsal  cirri  and  the  knob-like  notopodium  with  the  short 
unjointed  setae.     There  is  no  neuropodium. 

4.  Identify  the  pharynx,  gizzard,  and  intestine. 

5.  Compare  the  sexual  bud  with  the  non-sexual  individual. 
The  adult  male  and  female  differ.     The  outer  prostomial  tenta- 


LEPIDONOTUS    SQUAMATUS.  89 

cles  of  the  male  are  forked.  Is  this  bud  to  be  a  male  or  a  female? 
In  an  older  sexual  individual  make  out  a  so-called  thoracic  region 
in  which  the  setae  are  short,  and  an  abdominal  region  in  which 
the  setae  are  long.  Look  for  evidences  of  germ  cells  in  the  body- 
cavity,  between  the  intestine  and  body-wall.  There  is  a  ventral 
brood-pouch  on  the  adult  female  and  the  young  partly  develop 
in  it.  Find  the  anal  cirri. 

A  drawing  illustrating  the  method  of  reproduction  should  be 
made. 

LEPIDONOTUS  SQUAMATUS. 

The  family  Polynoidse,  to  which  this  belongs,  can  be  distin- 
guished from  all  others  by  the  presence  of  peculiar  plates  (elytra) 
on  the  dorsal  surface.  They  lead  sluggish  lives  under  stones 
and  are  carnivorous.  Note  the  size,  color,  and  shape  of  the 
worm. 

1.  The  elytra.    How   are   they   arranged?     What   purpose 
do  they  serve?    How  many  are  there?     With  a  hand-lens  ob- 
serve the  fringed  condition  of  the  outer  edge  and  the  small  tuber- 
cles covering  the  surface.     Note  the  color  of  the  elytra  and  the 
notches  in  the  inner  edges  of  the  posterior  pair.     L.  sublcevis 
differs  in  that  its  elytra  are  merely  punctate  and  the  posterior 
pair  are  not  so  deeply  notched. 

2.  The  head  is  hidden  by  the  first  pair  of  elytra.     If  the  ely- 
tra are  removed  you  will  find  a  small  reddish  prostomium  with 
two  pairs  of  eyes,  three  tentacles  (the  middle  one  large  and  club- 
shaped),  and  a  pair  of  palps. 

3.  Find  the  mouth,  which  is  placed  ventrally.     Note  the 
median,  red  streak  along  the  ventral  surface  that  is  due  to  pig- 
mented  cells  which  surround  the  nerve  cord.     If  the  pharynx 
is  everted,  observe  the  fringe  of  papillae  surrounding  a  dorsal 
and  a  ventral  pair  of  teeth.     There  are  no  septa  in  the  anterior 
region  of  the  body  where  the  withdrawn  pharynx  lies. 

4.  The  anus  is  dorsally  placed,  and  can  be  found  beneath  the 
notches  in  the  last  pair  of  elytra. 

A  drawing  is  desirable. 


90  ANNELIDA. 


DIOPATRA  CUPREA. 

This  worm  belongs  to  the  family  Eunicidse.  Specimens 
live  on  mud-  and  sand-flats,  sometimes  above  low-tide  mark, 
but  usually  where  the  burrows  are  covered  by  water.  This 
form  is  especially  interesting  because  of  its  feeding  and  tube- 
building  habits,  parapodial  gills,  and  complex  jaw-apparatus. 
Study  the  preserved  specimens  for  the  structure  and  specimens 
in  an  aquarium  for  the  habits.  Notice  the  construction  of  the 
tube  and  determine  how  it  is  formed. 

1.  Notice  the  size  of  the  body,  also  its  gradual  attenuation 
posteriorly.    Account  for  this  condition.     Observe  how  degen- 
erate the  parapodia  are  posteriorly  from  the  same  cause. 

2.  The  prostomium.    Identify  the  tentacles.    What  is  their 
number  and  arrangement?     Find  a  pair  of  eyes  dorsally  placed 
behind  the  tentacles,  also  a  pair  of  palps  in  front  of  them.     Note 
a  second,  larger  pair  of  palps  which  serve  as  an  upper  lip. 

3.  The  peristomium.     What  appendages  does  it  carry  ?    Note 
the  lower  lip  formed  from  the  ventral  edge  of  the  peristomium. 

4.  The  position  of  the  jaw-apparatus  can  be  identified  as  being 
in  a  pouch  ventral  to  the  buccal  region.     Find  both  by  means 
of  a  probe.     What  kind  of  food  are  such  jaws  fitted  for? 

5.  The  parapodia  vary  greatly,  depending  upon  their  posi- 
tion on  the  body.     Notice  that  the  notopodia  are  vestigial, 
being  represented  only  by  the  dorsal  cirri  and,  toward  the  ante- 
rior end,  branchial  cirri  or  gills.    Acicula  can  be  seen  projecting 
into  the  base  of  the  dorsal  cirrus.    The  neuropodium  shows  two 
kinds  of  setae:  (a)  stiff  and  unjointed,   (b)   crochets.     It  also 
bears  an  accessory  cirrus  and  the  ventral  cirri,  which  are  curiously 
modified  in  most  cases  as  glands  for  use  in  tube-building.    Make 
out  all  these  modifications  and  where  they  occur. 

CHAETOPTERUS. 

This  is  one  of  the  most  aberrant  of  our  Polychsetse.  It  lives 
on  mud-flats  below  low  tide  in  a  U-shaped,  parchment-like  tube, 
both  ends  of  which  protrude  above  the  sand.  In  the  body 


AMPHITRITE   ORNATA.  91 

three  regions  can  be  distinguished.  Examine  a  tube  and  see 
the  size  of  its  outer  openings.  Specimens  may  be  made  to  live 
in  tubes  of  glass,  bent  to  correspond  to  their  tubes,  and  their 
normal  movements  may  thus  be  studied  in  aquaria.  What 
must  be  the  source  of  the  animal's  food. 

1.  The  anterior  region.    Identify   ten  modified   parapodia, 
the  fourth  of  which  is  supplied  with  a  group  of  much  stouter 
setse.     Observe  that  the  funnel-like  mouth  is  placed  dorsally 
and  surrounded  ventrally  and  laterally  with  flaring  peristomial 
lips.     Find  the  pair  of  peristomial  cirri.     The  region  between 
these  cirri  represents  the  prostomium. 

2.  The  middle  region   consists   of    five   somites.     The  first, 
the  eleventh  segment,  is  marked  by  the  great  pair  of  wings 
which  are  used  to  bring  food  to  the  mouth.     Their  dorsal  sur- 
faces are  grooved  and  supplied  with  cilia,  as  is  the  median  dorsal 
line.     Hence  a  current  of  water  passes  continually  toward  the 
mouth.     The  twelfth  somite  is  marked  by  a  dorsal  and  a  ven- 
tral sucker,  which  are  modified   parapodia.     Somites  thirteen, 
fourteen,  and  fifteen  carry  notopodial  folds  or  fans,  for  keeping 
up  a  stream  of  water  through  the  tube.     Their  neuropodia  are 
mere  knobs. 

3.  The   posterior  region  is   less   highly   modified.     Of  how 
many  segments  does  it  consist?     Notice  their  gradual  diminu- 
tion in  size.     Homologize  the  parts  of  their  appendages. 

4.  The  living  Chaetopterus  contains  a  green  coloring-matter 
and  is  very  phosphorescent.    A  commensal  polynoid  often  lives 
in  its  tube. 

A  drawing  is  desirable. 

Lillie:  Observations  and  Experiments  Concerning  the  Elementary  Phe- 
nomena of  Embryonic  Development  in  Chsetopterus.  Jour.  Exp.  Zool., 
3,  1906. 

AMPHITRITE  ORNATA. 

This  belongs  to  the  family  Terebellidse  and  lives  under  stones, 
or  in  mud  or  sand,  along  shore  in  stout  muddy  tubes. 

1.  Find  the  prostomium,  which  forms  an  upper  lip  and  bears 
a  transverse  group  of  long,  retractile  tentacles. 


92  ANNELIDA. 

2.  The  peristomium  forms  the  under  lip,  but  bears  no  appen- 
dages. 

3.  Find  three  pairs  of  ramose  gills.    These  are  modifications 
of  the  dorsal  cirri.     (Terebella  has  three  pairs,  but  they  are  of 
unequal  size.) 

4.  Notice  again  the  feeble  development  of   the  parapodia 
and  the  absence  of  ventral  cirri  and   neuropodial  sets.    Setae 
are  not  found  posteriorly.     On  what  somite  do  they  begin? 

5.  Find  the  ventral  shield  glands  which  are  concerned  in 
building  the  tube.    How  many  are  there? 

6.  The  live  worm  is  of  a  bright  pinkish  color,  due  to  its  red 
blood.     There  is  only  one  internal  septum  and  it  forms  a  so- 
called  diaphragm.     Anterior  to  the  diaphragm  the  nephridia 
are  large  and  excretory  in  function.     Posterior  to  the  diaphragm 
the  nephridia  serve  as  genital  tubes. 

A  drawing  is  desirable. 

CISTENIDES  GOULDII. 

This  very  aberrant  worm  belongs  to  the  family  Amphictenidae. 

1.  Study  the  beautiful  tube  of  sand  and  the  manner  in  which 
the  grains  are  fitted  together.     It  is  said  that  the  worms  can 
carry  the  tubes  about. 

2.  See  how  the  peristomium  and  the  large  golden  setae  close  the 
shell.    The  sets  are  said  to  belong  to  the  second  somite.     Notice 
the  ends  of  the  tentacles  protruding  from  the  tube. 

3.  Find  the  tentacles,  two  pairs  of  gills,  and  the  parapodia. 
Notice  how  the  latter  diminish  in  size  posteriorly  and  how  each 
typically  consists  of  a  ridge-like  notopodium  without  set®  and  a 
reduced  neuropodium  with  long  golden  seta3.     If  the  specimen  is 
complete  you  can  see  a  much  degenerated  portion  (the  scapha) 
at  the  posterior  end,  which  serves  to  close  the  small  end  of  the 
tube. 

A  drawing  is  desirable. 

CLYMENELLA  TORQUATA. 

This  worm  belongs  to  the  family  Maldanidae.  It  makes 
tubes  of  sand  and  generally  lives  in  sheltered  places  on  sandy  or 
muddy  shores. 


ARENICOLA  CRISTATA.      SABELLA  MICROPHTHALMA.          93 

1.  Study  the  structure  of  the  tube;  observe  how  the  animal 
protrudes  at  either  end  of  the  tube. 

2.  Observe  the  diameter  and  length  of  the  worm,  the  small 
number  of  somites,  their  great  length  as  compared  to  somites 
of  Nereis,  and  the  reduced  parapodia  provided  with  simple  setae. 
Notice  the  characteristic  collar  on  the  fifth  somite,  and  the 
funnel  at  the  posterior  end,  with  the  anus  within  it.    The  mouth 
is  more  or  less  ventral  and  is  overhung  by  a  narrow  prostomium 
surrounded  by  a  peristomial  rim. 

A  drawing  is  desirable. 

ARENICOLA  CRISTATA. 

This  remarkable  worm,  called  the  " lug- worm"  by  fisher- 
men, belongs  to  the  family  Arenicolidae. 

1.  Notice  the  color,  and  the  gradual  diminution  in  size  pos- 
teriorly.   Also  notice  the  false  annulations  between  the  appen- 
dages, the  arborescent  gills  representing  modifications  of  certain 
notopodia,  the  reduced  parapodia,  and  the  character  of  the  setae. 

2.  If  the  buccal  region  is  everted,  observe  the  papillae  which 
cover  it.    The  prostomium  is  an  inconspicuous  dorsal  knob  and 
it  is  fused  with  the  peristomium.    At  the  sides  of  the  prostomium 
is  the  ciliated  nuchal  groove. 

3.  On  what  somites  can  you  find  indications  of  neuropodia? 
of  gills?  of  setae?    Notice  the  cirriform  papillae  of  the  "tail." 
Find  large  nephridiopores  on  certain  somites  about  an  eighth 
of  an  inch  below  each  notopodium.     What  is  the  distribution  of 
the  pores? 

A  drawing  is  desirable. 

SABELLA  MICROPHTHALMA. 

This  worm  belongs  to  the  family  Sabellidae.  It  builds  leath- 
ery, muddy  tubes  on  piles,  among  tunicates,  algae,  etc. 

1.  In  addition  to  the  general  size,  form,  and  color  of  the 
worm,  observe  the  reduced  condition  of  the  parapodia,  and  the 
arrangement  and  general  structure  of  the  branchice  or  gitts.  These 
structures  are  modifications  of  the  palps  and  not  of  the  parapo- 
dia, as  in  the  other  species  which  have  been  studied.  Observe 


94  ANNELIDA. 

the  two  irregular  rows  of  small  ocelli  or  eye-spots.  Account 
for  the  presence  of  eyes  in  their  position.  A  pair  of  short  tenta- 
cles can  be  seen  by  spreading  the  branchiae  aside. 

2.  Find  a  collar  which  is  used  in  smoothing  the  orifice  of  the 
tube.    This  is  a  peristomial  structure  and  is  so  extensively 
developed  in  some  species  as  to  hide  the  prostomium  entirely. 

3.  Identify   eight   setigerous   somites    anteriorly,  in  which 
the  capillary  setce  are  in  the  notopodium  and  the  uncini  are  in 
the  neuropodium.     With  the  peristomium  they  form  a  "  thorax" 
of  nine   somites.     In   the   somites  which  follow,  the  "abdo- 
men," observe  that  the  uncini  and  the  capillary  setae  stand  in 
the  reverse  order. 

4.  Find    the    ventral    shield-glands.     A    furrow    (sulcus    or 
fsecal  groove)  divides  them  into  pairs  toward  the  posterior  end 
of  the  worm. 

A  drawing  is  desirable. 

HYDROIDES. 

This  is  a  member  of  the  family  Serpulidse.  Study  living 
specimens  and  their  heavy  calcareous  tubes.  Notice  the  banded 
branchice  (modified  palps)  and  the  dorsally  placed  operculum,  a 
modified  gill  filament.  Look  for  "eyes"  on  the  gill  filaments. 

A  drawing  is  desirable. 

Hatschek:   Entwicklung   der   Trochophora   von   Eupomatus   uncinatus, 
Philippi.     (Serpula  uncinata.)     Arb.  Zool.  Ins.,  Wien,  6,  1886. 

SPIRORBIS  BOREALIS. 

This  animal  is  also  a  member  of  the  family  Serpulidse. 
Specimens  are  very  abundant  along  the  shore,  attached  to  Fucus. 

1.  Study  the  tube  and  notice  the  way  in  which  it  "parallels" 
the  form  of  a  small  snail-shell. 

2.  Remove  a  live  specimen  from  the  Fucus  on  which  it  grows 
and  crack  the  tube  away  with  a  needle.     Study  the  animal  in 
a  watch-glass  with  a  low  power.     Identify  the  gills,  the  opercu- 
lum (which  serves  as  a  "brood-pouch"),  the  setce,  and  the  collar. 
Are  there  any  "eyes"  on  the  gills? 


PHASCOLOSOMA.  95 

3.  Study  the  egg-strings  which  are  lodged  in  the  tube,  and 
the  young  embryos  which  are  to  be  found  in  the  brood-pouch. 
A  drawing  is  desirable. 


GEPHYREA. 

PHASCOLOSOMA. 

This  form  is  commonly  found  buried  in  sand  between  tide- 
marks.  Specimens  sometimes  occur  on  the  same  flats  with 
Nereis,  but  they  are  generally  more  abundant  where  the  mud  is 
of  a  slightly  different,  more  sticky  character. 

1.  Handle  a  living  specimen  and  see  how  turgid  it  is.    If 
you  touch  a  specimen  that  has  been  allowed  to  expand  in  a  dish 
of  sea-water  you  will  find  it  is  rather  soft,  but  becomes  turgid 
immediately  upon  being  touched.     How  is  this  accomplished? 

2.  Examine  a  living  animal  in  a  dish  of  sea-water.     The 
anterior  portion  of  the  body,  the  introvert,  is  drawn  in,  but  may 
occasionally  be  extended,  when  it  will  be  seen  to  bear  at  the 
anterior  extremity  a  crescentric  crown  of  tentacles,  which  partly 
surrounds  the  mouth. 

3.  Compare  with  a  preserved  specimen  which  has  been  killed 
with  the  introvert  extended. 

Make  drawings  showing  the  animal  with  the  introvert  pro- 
truded and  with  the  introvert  concealed. 

4.  The  anus  is  located  on  a  dorsal  papilla,  anterior  to  the 
middle  of  the  body.     Near  the  anus  a  pair  of  lateral  papillae 
mark  the  position  of  the  nephridiopores.     The  coiled  intestine 
and  brown  nephridial  tubes  can  probably  be  seen  through  the 
body-wall.    Note  carefully  the  character  of  the  skin.     Is  there 
any  indication  of  spines,  appendages,  or  eye-spots? 

For  dissection  use  both  fresh  and  preserved  specimens. 
With  scissors  open  the  worm  from  end  to  end  near  the  mid- 
dorsal  line,  and  pin  the  body-wall  out  flat. 

5.  In  opening  the  fresh  worm,   note  the  pinkish  ccelomic 
fluid  which  fills  the  ccelom.    Examine  a  drop  under  the  micro- 
scope.   What  functions  has  this  fluid  to  perform? 


96  ANNELIDA. 

Alimentary  Canal. — Trace  the  alimentary  canal  (stomach- 
intestine)  from  mouth  to  anus.  Do  any  digestive  glands  open 
into 'it  at  any  point?  Note  the  mesenterial  thread  which  runs 
through  the  axis  of  the  intestine  spiral.  Where  is  it  attached? 
Does  it  seem  to  be  contractile  in  the  fresh  worm? 

Muscular  System. — Note  the  silvery-white  longitudinal 
muscles  composing  the  inner  layer  of  the  body-wall.  Are  they 
arranged  in  distinct  bands  or  in  a  continuous  sheet?  Remove 
some  of  these  muscles  carefully  to  expose  the  layer  of  circular 
muscles.  How  many  retractor  muscles  of  the  introvert  are  there? 
How  is  the  mechanism  of  protrusion  of  the  introvert  to  be  ex- 
plained? 

Circulatory  System. — This  system  is  very  difficult  to  ob- 
serve. Dorsal  and  ventral  blood-sinuses  are  present,  and  com- 
municate anteriorly  by  a  circular  sinus.  A  blood-sinus,  purplish 
red  in  living  specimens,  occurs,  as  an  irregular  tube,  along  the 
anterior  portion  of  the  esophagus  and  intestine. 

Excretory  System. — Find  a  pair  of  brown  nephridia,  an 
inch  or  more  in  length.  Cut  off  a  nephridium  (from  the  fresh 
worm)  as  close  as  possible  to  the  body-wall,  and  examine  it 
under  a  microscope.  Near  the  cut  (the  attached)  end  find  the 
coelomic  opening  or  nephrostome.  Is  it  ciliated? 

Reproductive  System. — The  sexes  are  separate.  Oogonia 
and  spermatogonia  are  detached  from  the  coelomic  epithelium, 
at  the  points  where  the  ventral  retractor  muscles  are  attached 
to  the  body-wall.  These  cells  become  detached  and  mature 
while  floating  in  the  ccelomic  fluid.  They  pass  out  through 
the  nephridia,  which  function  as  gonoducts. 

Nervous  System. — Does  the  ventral  nerve-cord  seem  to  be 
double?  Is  it  ganglionated?  Does  it  give  off  lateral  nerve 
branches?  Trace  the  circum-esophageal  connectives  to  the  supra- 
esophageal  ganglion.  The  ganglion  is  small  and  situated  behind 
the  crown  of  tentacles,  to  which  sensory  nerves  extend.  Does 
any  system  of  organs  show  segmentation? 

Make  a  drawing  to  show  the  internal  anatomy. 

Gerould:  The  Development  of  Phascolosoma.     Zool.  Jahrb.,  23,  1906. 
C.  B.  Wilson:  Our  North  American  Echiurids.    Biol.  Bui,  1,  1900. 


MOLLUSCA* 

Unsegmented.    Usually   provided   with   a   calcareous   pro- 
tecting shell  and  a  ventral  foot. 

CLASS  1.  Lamellibranchiata. 

Bivalve  shell.  Gills  adapted  for  gathering  food 
as  well  as  for  respiration.  Foot  usually  adapted 
for  burrowing.  No  hard  mouth  parts. 

Order  1.  Protobranchia. 

Gills  composed  of  a  series  of  transverse  plates. 
Foot  apparently  split  at  the  end.  Two  adductor 
muscles,  posterior  frequently  the  smaller.  (Nu- 
cula,  Yoldia.) 

Order  2.  Filibranchia. 

Gills  lamelliform.  Filaments  united  by  modified 
cilia.  Anterior  adductor  muscle  frequently 
greatly  reduced.  (Mytilus,  Modiola.) 

Order  3.  Pseudo-lamellibranchia. 

Gills  lamelliform.  Inter-filamentar  junctions 
usually  not  very  extensive,  may  be  either  ciliary 
or  vascular.  Only  one  adductor  muscle.  (Pec- 
ten,  Ostrea.) 

Order  4.  Eulamellibranchia. 

Gills  lamelliform.  Inter-filamentar  junctions 
extensive  and  vascular.  Adductor  muscles  of 
nearly  equal  size.  (Venus,  Unio,  Mya.) 

Order  5.  Septibranchia. 

Gills  reduced  to  a  horizontal  partition.    Two  ad- 
ductor   muscles.    Deep    sea    forms.      (Silenia, 
Cuspidaria.) 
CLASS  2.  Amphineura. 

Bilaterally  symmetrical,  elongated.  Nervous 
system  not  concentrated.  Radula  sometimes 
present.  Shell,  when  present,  composed  of 
eight  transverse  pieces. 

Order  1.  Placophora. 

Dorsal  shell,  composed  of  eight  transverse  pieces. 
7  97 


98  MOLLUSCA. 

Foot  broad.  Gills  simple,  lateral.  (Chiton, 
Chsetopleura,  Trachydermon.) 

Order  2.  Aplacophora. 

Body  elongated,  covered  by  a  mantle.    Adult 
without  shell  but  with  spicules.     No  true  foot. 
Gills  posterior.     (Neomenia,  Dondersia.) 
CLASS  3.  Gastropoda. 

Body  unsymmetrical,  usually  covered  by  a  spiral 
shell.    Foot  usually  flattened  and  adapted  for 
creeping.    Radula  usually  present. 
Subclass  1.  Streptoneura. 

Nervous  system  twisted  into  the  form  of  a  figure 
8.  Sexes  distinct. 

Order  1.  Aspidobranchia. 

Nervous  system  not  concentrated.  Gills  usually 
present  and  paired.  Auricles  paired.  (Acmaea, 
Patella,  Haliotus.) 

Order  2.  Pectinibranchia. 

Nervous  system  somewhat  concentrated.     Single 
gill.     Single  auricle.      (Buccinum,  Crepidula, 
Fulgur.) 
Subclass  2.  Euthyneura. 

Nervous  system  not  twisted  into  the  form  of  a 
figure  8.  Sexes  united. 

Order  1.  Opisthobranchia. 

Aquatic  respiration.  Shell  when  present  rather 
delicate.  (Bulla,  ^Eolis.) 

Order  2.  Pulmonata. 

Air-breathers.     Live  on  land  or  in  fresh  water. 
Aperture  to  mantle  cavity  narrow  and  contrac- 
tile.    (Limax,  Limnsea,  ;Helix.) 
CLASS  4.  Scaphopoda. 

Bilaterally  symmetrical.      Shell   tubular,  elon- 
gated dorso-ventrally  and  open  at  both  ends. 
Foot  conical.     (Dentalium.) 
CLASS  5.  Cephalopoda. 

Bilaterally  symmetrical.     Shell  chambered  or  re- 
duced and  internal.     Distinct  head  with  arms 
bearing  suckers. 
Subclass  1.  Dibranchiata. 

Arms  forming  a  circlet  around  the  mouth.  Fun- 
nel a  complete  tube.  Shell  usually  internal. 
Two  gills. 


VENUS  MEECENAKIA.  99 

Order  1.  Decapoda. 

Ten  arms,  two  of  which  are  elongated,  suckers 
on  stalks.  (Loligo,  Sepia>  Spirula.) 

Order  2.  Octopoda. 

Eight  arms,  suckers  sessile.      (Octopus,  Argo- 
naut a.) 
Subclass  2.  Tetrabranchiata. 

Tentacles  numerous.  External  chambered  shell. 
Funnel  open  along  one  side.  Only  one  living 
genus.  (Nautilus.) 

Brooks:  The  Origin  of  the  Oldest  Fossils  and  the  Discovery  of  the  Bottom 

of  the  Ocean.     Smithsonian  Kept.,  1894. 
Kellogg:  Contribution  to  our  Knowledge  of  the  Morphology  of  Lamelli- 

branchiate  Mollusks.     Bui.  U.  S.  Fish  Com.,  1890. 

:  Shell-fish  Industries.     Henry  Holt  and  Co.,  1910. 

Pelseneer:  Contribution  a  L'Etude  des  Lamellibranches.     Arch.  d.  Biol., 

11,  1891. 
:  Recherches  Morphologiques  et  Phyloge'ne'tiques  sur  les  Mollusques 

Archaiques.     Acad.  roy.  d.  Sci.  d.  letters  et  d.  beaux-arts  d.  Belgique, 

1899. 
:  £tude  sur  des  Gastropodes  Pulmone*s.     Mem.  Acad.  roy.  d.  Sci.  d. 

letters  et  d.  beaux-arts  de  Belgique,  1901. 
Ridewood:  On  the  Structure  of  the  Gills  of  Lamellibranchs.     Phil.  Trans. 

Roy.  Soc.,  London,  B,  195,  1903. 
Stenta:  Zur  Kenntnis  der  Stromungen  im  Mantelraume  der  Lamellibran- 

chiaten.    Arb.  Zool.  Inst.  Univ.  Wien.,  14,  1902. 


LAMELLIBRANCHIATA. 

VENUS  MERCENARIA.  (Qaahog.)1 

Animals  of  this  species  wander  around  over  muddy  bottoms 
in  rather  shallow  water,  keeping  the  siphon  end,  at  least,  above 
the  surface  of  the  mud.  If  possible,  you  should  find  specimens 
in  their  native  places  and  watch  their  movements.  Specimens 
placed  in  water  and  left  undisturbed  for  some  hours  are  likely 
to  protrude  the  siphons,  and  the  foot  may  be  protruded  in  some 
cases.2  Allow  powdered  carmine  to  slowly  settle  past  the  open- 

1  Points  in  which  the  fresh-water  mussel  differ  have  been  noted,  so  the 
directions  may  be  used  for  that  form. 

2  Other  species  of  lamellibranchs  are  more  satisfactory  than  Venus  for 
studying  movements,  as  they  expand  quickly  after  being  disturbed.    Among 
the  common  ones  that  may  be  mentioned  are  Ensis,  Cumingia,  Yoldia, 
and  Mytilus. 


100  MOLLUSCA. 

ings  of  the  siphons  and  determine  the  direction  of  the  current 
of  water  for  each.  Touch  portions  of  the  animal  and  find  what 
parts  are  most  sensitive. 

Shell. — Note  its  general  shape,  and  that  it  is  composed  of 
two  symmetrical  parts,  the  valves.  For  each  valve  notice: 

1.  The  outline. 

2.  A  swelling,  the  umbo,  ending  in  a  point,  the  beak,  from 
which  growth  has  proceeded. 

3.  The  lines  of  growth.    Were  the  valve  cut  off  along  one  of 
these  lines,  the  shape  would  not  be  changed.     Why  are  the  lines 
arranged  in  this  manner?    How  were  they  formed? 

The  two  valves  are  joined  by  the  ligament.  The  margin 
bearing  the  ligament  is  dorsal,  and  that  toward  which  the  beaks 
point  is  anterior.  Which  valve  is  right  and  which  is  left? 

Draw  a  valve,  showing  the  points  observed. 

Pry  the  two  valves  apart  and  insert  a  knife-blade  between 
the  mantle  and  one  valve  of  the  shell.  Notice  that  the  lobes 
of  the  mantle  are  loosely  attached  to  the  shell  along  their  mar- 
gins, and  more  firmly  attached  a  half  inch  or  more  from  the 
margins. 

Separate  the  mantle  from  one  valve,  and  cut  the  adductors 
where  they  are  attached  to  this  valve.  Why  do  the  valves  gape 
now?  Press  them  together,  and  notice  that  they  stay  closed 
only  while  held.  Remove  a  valve  and  study  its  interior. 

1.  Find  the  large  scars  where  the  anterior  and  posterior  ad- 
ductor muscles  were  attached. 

2.  Find  smaller  scars  where  the  anterior  and  posterior  foot 
muscles  were  attached.    The  anterior  scar  is  dorsal  and  a  little 
posterior  to  the  corresponding  adductor  muscle  scar.     (Not  the 
position  for  Unio.)     The  posterior  scar  connects  with  the  dorsal 
portion  of  the  corresponding  adductor  muscle  scar. 

3.  The  ventral  borders  of  the  adductor  muscle  scars  are  con- 
nected by  a  distinct  line,  the  pallial  line.     What  forms  it?    The 
posterior  end  of  this  line  is  indented  to  form  the  pallial  sinus. 
(Not  true  for  Unio.)     What  is  the  meaning  of  this  sinus? 


VENUS   MERCENARIA.  101 

4.  Along  the  dorsal  margin  of  the  valve  notice  prominences, 
the  teeth.    There  are  two  kinds  of  teeth.     The  anterior,  cardi- 
nal, consist  of  short  elevations.     The  posterior,  lateral,  are  not 
very  prominent,  but  are  comparatively  long  and  extend  along 
the  dorsal  margin.     Notice  that  the  teeth  on  the  two  valves 
interlock.    What  is  their  function  ? 

Draw  a  valve  as  seen  from  the  inside. 

5.  By  examining  the  inside  of  a  shell  of  Unio  or  Mytilus  near 
its  margin,  the  typical  three  layers  of  which  it  is  composed  can 
be  seen.     How  is  it  possible  for  all  three  layers  to  be  secreted 
by  the  mantle,  which  lines  the  inside  of  the  shell  ?    Can  you  find 
any  reason  for  more  than  one  layer? 

Mantle. — This  consists  of  two  lobes  (one  of  which  is  normally 
applied  to  the  inner  surface  of  each  valve  of  the  shell)  that  are 
united  dorsally. 

1.  The  free  border  of  each  lobe  is  thickened,  and  contains 
muscles  that  were  attached  to  the  shell  along  the  pallial  line. 
What  function  do  these  muscles  perform? 

2.  The  posterior  portions  of  the  lobes  of  the  mantle  are 
thickened  and  united  to  each  other  so  as  to  form  two  tubes  (in 
Unio  the  ventral  tube  is  formed  by  contact  only),  the  siphons, 
through  which  water  passes  into  and  out  of  the  shell. 

3.  See  how  the  muscles  of  the  siphons  are  arranged  and  at- 
tached.    Does  the  attachment  bear  any  relation  to  the  pallial 
sinus  in  Venus? 

Visceral  Mass  and  Foot. — These  portions  form  the  large 
median  mass.  The  viscera  are  contained  in  the  dorsal  portion. 

1.  The  ventral  portion  is  hard  and  muscular,  and  forms  the 
foot. 

2.  Besides  the  crossing  muscle  fibers  of  which  the  foot  is 
largely  composed,  it  is  supplied  with  two  pairs  of  muscles  that  are 
attached  to  the  shell.    The  cut  ends  of  these  muscles,  the  an- 
terior and  the  posterior  foot  muscles,  may  be  seen  protruding 
through  the  lobe  of  the  mantle.    They  correspond  in  position 
to  the  scars  on  the  shell. 

Do  you  understand  by  what  means  the  foot  is  protruded  ? 


102  MOLLUSCA. 

Gills. — These  consist  of  two  pairs  of  thin,  striated,  some- 
what brownish  organs,  a  pair  lying  on  each  side  of  the  visceral 
mass,  between  it  and  the  lobes  of  the  mantle. 

1.  Each  gill  extends  from  the  wall  that  separates  the  two 
siphons,  anteriorly  and  dorsally  to  a  point  nearly  opposite  the 
beaks  of  the  shell,  and  is  attached  by  its  dorsal  margin  only. 

2.  Each  outer  gill  is  attached  along  its  dorsal  border  to  the 
corresponding  mantle  lobe  on  the  outer  side.     The  inner  gills, 
besides  being  attached  to  the  dorsal  margins  of  the  outer  gills, 
are  on  their  inner  sides  attached  to  each  other  and  to  the  vis- 
ceral mass.     (For  some  distance  the  inner  side  of  the  inner  gill 
lies  against  the  visceral  mass,  but  is  not  attached  to  it.) 

By  this  arrangement  the  space  between  the  lobes  of  the 
mantle,  which  is  known  as  the  mantle  chamber,  is  divided  into  a 
ventral  and  a  dorsal  portion.  The  ventral  portion  is  much 
the  larger,  communicates  with  the  ventral  siphon,  and  because 
the  gills  hang  into  it,  it  is  known  as  the  branchial  chamber.  The 
dorsal  chamber  is  known  as  the  cloacal  chamber.  The  siphons 
are  frequently  referred  to  by  names  corresponding  to  the  cham- 
bers with  which  they  communicate.  The  minute  structure  of 
the  gills  will  be  studied  later. 

3.  Place  a  little  powdered  carmine  on  the  gill  of  a  specimen 
that  is  submerged  in  sea-water  and  see  what  becomes  of  it. 

Labial  Palps. — These  consist  of  a  pair  of  rather  small  tri- 
angular flaps  on  each  side  of  the  visceral  mass. 

1.  The  two  outer  palps  are  united  above  the  mouth,  which 
is  situated  just  posterior  to  the  dorsal  border  of  the  anterior 
adductor  muscle,  and  form  a  small  fold  that  corresponds  in 
position  to  an  upper  lip. 

2.  The  two  inner  palps  likewise  unite  to  form  a  fold  corre- 
sponding in  position  to  an  under  lip. 

Make  a  drawing  showing  the  arrangement  of  the  soft  parts. 

Structure  of  a  Gill. — Cut  off  a  piece  of  the  edge  of  a  gill,  put 
it  on  a  slide  with  a  drop  of  sea-water,  and  examine  with  a  low 
power  of  the  microscope.  Notice: 

1.  The  cilia  on  the  edge  and  surface  of  the  gill. 


VENUS   MERCENABIA.  103 

2.  The  surface  is  marked  by  a  series  of  parallel  ridges,  the 
filaments,  with  grooves  between  them.1 

The  filaments  are  joined  together  laterally  by  series  of  bridges 
(you  will  see  them  later),  the  inter-filamentar  junctions,  with 
the  pores,  inhalant  ostia,  between  them.  Each  side  of  the  gill 
is  thus  composed  of  a  single  layer  of  united  parallel  filaments, 
which  together  form  what  is  known  as  a  lamella.  Each  gill  is 
composed  of  two  such  lamellsB,  one  on  each  side.  These  lamellae 
are  united  at  intervals  by  bridges  that  run  the  whole  width  of 
the  gill  (dorsal  to  ventral),  parallel  to  the  filaments,  and  at 
right  angles  to  the  inter-filamentar  junctions.  These  are  called 
the  inter-lamellar  junctions.  By  means  of  the  inter-lamellar 
junctions,  the  space  between  the  two  lamellae  is  divided  into  a 
series  of  water  tubes.  The  openings  of  these  tubes  into  the 
cloacal  chamber  may  easily  be  seen  after  the  cloacal  chamber 
has  been  cut  open. 

3.  Separate  a  small  piece  of  one  lamella  from  the  other. 
This  can  most  readily  be  done  by  catching  the  free  dorsal  bor- 
der of  the  inner  lamella  of  an  inner  gill  with  the  forceps,  and 
either  tearing  off  a  piece  or  freeing  it  by  cutting  with  scissors 
while  it  is  being  removed  with  the  forceps.     Mount  this  piece, 
with  the  outer  surface  up,  without  pressing  it,  under  a  cover- 
glass  in  a  drop  of  sea- water  and  observe  with  a  low  power: 

(a)  Filaments,  that  run  the  width  of  the  gill. 
(6)  Inter-filamentar  junctions,  which  form  bridges  connect- 
ing the  filaments. 

(c)  Inhalant  ostia.     The  opening  bounded  by  filaments  and 
inter-filamentar  junctions. 

(d)  The  position  of  the  torn  inter-lamellar  junctions,  appear- 
ing as  indefinite  dark  stripes  running  in  the  same  direction  as 
the  filaments. 

With  a  high  power  observe : 

(a)  The  chitinous  rods  that  lie  inside  of,  and  stiffen  the 
filaments. 

1  The  general  surface  features  are  especially  easily  seen  in  Pecten, 
where  the  inter-filamentar  junctions  are  small  and  well  marked,  and  the 
inhalant  ostia  are  correspondingly  large  and  distinct. 


104  MOLLUSCA. 

(6)  The  cilia  on  the  sides  of  the  filaments.  These  are  of 
two  kinds:  (1)  Surface  cilia  that  form  currents  of  water  along 
the  filaments.  These  will  be  seen  waving  back  and  forth,  or 
if  still  moving  rapidly,  apparently  moving  along  the  sides  of 
the  filaments.  (2)  Deeper  cilia  that  are  down  between  the 
filaments  and  can  be  seen  by  changing  the  focus.  These  move 
at  right  angles  to  the  others,  and  apparently  become  longer  and 
shorter.  Why? 

Draw  a  surface  view  of  a  piece  of  a  lamella. 

Examine  a  piece  of  the  gill  of  Mytilus  for  the  above  struc- 
tures. In  this  form  the  inter-filamentar  junctions  are  small 
and  Composed  of  modified  cilia  only,  and  the  inhalant  ostia 
are  correspondingly  large.  By  pressing  the  gill  the  inter-fila- 
mentar junctions  can  be  pulled  apart. 

Study  prepared  sections  of  the  gill  of  Venus  and  notice: 

1.  Lamellae. 

2.  Inter-lamellar  junctions. 

3.  Water  tubes. 

4.  Filaments. 

5.  Inter-filamentar  junctions. 

6.  Cilia. 

7.  Inhalant  ostia. 

8.  Blood  spaces. 

9.  Chitinous  rods. 
Draw. 

Understand  the  direction  taken  by  water  in  passing  from  the 
branchial  to  the  cloacal  siphon.  What  makes  the  water  move? 

Labial  Palps. — The  positions  of  these  organs  have  already 
been  noted. 

1.  Examine  a  piece  of  the  palp  with  a  microscope,  and  notice 
that  the  side  turned  toward  the  adjacent  palp  is  thrown  into 
ridges  and  grooves,  and  is  densely  ciliated. 

2.  The  space  between  each  outer  and   inner   palp  is   con- 
tinuous with  the  "corners"  of  the  mouth.    The  free  margins 
come  close  to  the  borders  of  the  gills  and  normally  inclose  them. 

Understand  how  food  is  gathered  and  carried  to  the  mouth. 
Circulatory  System. — The  pericardium,  in  which  the  heart 


VENUS   MERCENARIA.  105 

lies,  is  a  somewhat  triangular  space  that  appears  clear,  through 
the  mantle.  It  lies  just  anterior  to  the  posterior  adductor 
muscle.  Open  the  pericardium,  and  notice  the  beating  of  the 
heart.  The  heart  consists  of  three  parts: 

1.  A  central  portion,  the  ventricle,  that  surrounds  the  intes- 
tine and  gives  rise  to  a  blood-vessel  at  each  end. 

2.  Two  triangular  portions,  the  auricles,  that  receive  blood 
from  the  gills  and  open  into  the  sides  of  the  ventricle. 

Notice  the  sequence  and  power  of  the  contractions. 

Just  posterior  to  the  pericardium  is  an  enlarged  portion  of 
the  alimentary  canal.  This  has  no  relation  to  the  heart,  for 
which  it  is  sometimes  mistaken. 

Excretory  and  Genital  Systems. — The  excretory  system  con- 
sists of  a  pair  of  dark  colored  glandular  organs  that  lie  beneath 
the  pericardium.  Each  communicates  with  the  pericardium 
by  a  small  opening  that  is  not  easy  to  demonstrate  in  dissections, 
and  with  the  cloacal  chamber  by  another  small  opening. 

By  turning  the  two  gills  (of  Venus)  dorsally  a  very  small 
papilla  may  be  seen,  just  beneath  the  free  border  of  the  inner 
gill,  lying  in  the  cloacal  chamber.  On  the  tip  of  this  papilla 
are  two  openings.  The  inner  one  is  the  opening  of  the  excretory 
organ.  The  outer  one  is  the  opening  of  the  genital  duct. 

The  genital  glands  are  light  colored  organs  that,  during  the 
breeding  season,  extend  through  the  principal  part  of  the  vis- 
ceral mass.  Neither  the  genital  nor  the  excretory  systems  can 
be  profitably  studied  in  a  general  dissection  of  this  form.  In 
Unio  the  excretory  organs  are  more  satisfactory  for  study.  Do 
you  understand  the  supposed  significance  of  their  connection 
with  the  pericardium? 

Nervous  System. — 1.  Carefully  remove  the  body-wall  by 
the  side  of  the  esophagus  and  notice  the  cerebral  ganglion  of  the 
corresponding  side.  This  is  a  rounded,  slightly  yellow  organ, 
about  the  size  of  a  pin-head,  lying  just  posterior  to  the  dorsal 
border  of  the  anterior  adductor  muscle.  (In  Unio  it  is  more 
ventral  in  position.)  The  cerebral  ganglia  of  the  two  sides  are 
united  by  a  commissure  that  passes  anterior  to  the  esophagus. 
Two  connectives  leave  each  cerebral  ganglion.  One  passes 


106  MOLLUSCA. 

posteriorly  to  join  the  visceral  ganglion  of  the  corresponding 
side.  The  other  passes  into  the  foot  to  join  the  pedal  ganglion 
of  the  corresponding  side. 

2.  Cut  the  united  lamella?  of  the  inner  gills  ventral  to  the 
posterior  adductor  muscle.     This  will  expose  the  visceral  ganglia. 
They  are  pear-shaped  bodies  lying  just  beneath  the  posterior 
adductor  muscle,  connected  with  each  other  by  a  short  com- 
missure, and  connected  with  the  cerebral  ganglia  by  connectives 
that  may  be  traced  a  short  distance  forward  without  dissection. 
A  large  nerve  leaves  the  posterior  end  of  each  ganglion  and 
supplies  the  posterior  end  of  the  corresponding  lobe  of  the  mantle. 
Smaller  nerves  go  to  the  posterior  adductor  muscle  and  gills. 

3.  With  a  razor  or  sharp  scalpel  make  a  median  sagittal 
section  of  the  foot,  extending  it  some  distance  into  the  visceral 
mass.     This  will  expose  the  pedal  ganglia,  that  lie  just  anterior 
to  a  loop  of  the  intestine,  and  dorsal  to  the  muscular  portion 
of  the  foot.     The  pedal  ganglia  are  connected  with  each  other 
by  a  broad  commissure  and  with  the  cerebral  ganglia  by  connec- 
tives. 

By  careful  dissection  it  is  possible  to  trace  the  connectives 
and  many  of  the  nerves.  The  razor  clam,  Ensis,  is  especially 
favorable  for  dissections  of  the  nervous  system,  as  the  ganglia, 
connectives,  and  many  important  nerves  lie  very  near  the 
surface  and  can  be  seen  without  cutting  the  tissues  above  them. 

Make  a  drawing,  indicating  the  position  of  the  ganglia. 

Digestive  System. — This  may  be  traced  by  following  a  guarded 
bristle  that  has  been  inserted  into  the  mouth  of  a  specimen  that 
has  been  killed  in  hot  water  (not  boiling),  or  by  very  carefully 
picking  off  the  tissue  from  one  side.  The  intestine  where  it 
penetrates  the  heart  has  already  been  seen,  and  may  easily  be 
followed  to  the  anus. 

The  general  arrangement  of  the  alimentary  canal  is  well 
shown  by  a  median  sagittal  section  of  a  preserved  specimen. 

The  brownish  digestive  gland,  commonly  called  the  "  liver," 
will  be  seen  surrounding  a  portion  of  the  stomach. 

The  enlargement  on  the  intestine  in  the  posterior  portion  of 
the  pericardium  is  of  unknown  function.  In  some  forms  a  special 


YOLDIA   LIMATULA.  107 

diverticulum  from  the  stomach  bears  a  transparent  cylindrical 
rod,  the  crystalline  style.  This  can  easily  be  found  in  Mya. 
Probably  all  lamellibranchs  have  similar  structures  more  or  less 
well  developed,  but  many  do  not  have  special  pouches  for  their 
formation. 

Draw  the  alimentary  canal.  (This  may  be  included  with 
your  sketch  of  the  nervous  system.) 

Cut  a  preserved  specimen  into  transverse  sections  about  a 
quarter  of  an  inch  thick,  and  place  the  sections  in  their  proper 
order  and  position.  (They  should  be  placed  in  a  dissecting  pan 
in  a  very  little  water.) 

Study  these  sections  for  the  arrangement  of  organs.  The 
relation  of  the  gills  to  the  branchial  and  the  cloacal  chambers 
should  be  understood. 

Make  drawings  of  sections  that  pass  through  the  heart  and 
through  the  posterior  adductor  muscle. 

If  time  permits,  it  will  be  desirable  to  become  acquainted  with 
some  of  the  structures  of  theoretic  importance  and  with  some 
of  the  adaptations  of  lamellibranchs  for  the  lives  they  live.  For 
this  purpose  a  few  forms  have  been  selected,  and  directions  for 
the  study  of  the  particular  parts  in  question  are  given. 

Belding:  A  Report  upon  the  Quahog  and  Oyster  Fisheries  of  Massachusetts. 

Fish  and  Game  Com.,  Mass.,  1912. 
Lefevre  and  Curtis:  Studies  on  the  Reproduction  and  Artificial  Propagation 

of  Fresh-water  Mussels.     Bui.  U.  S.  Bur.  Fish.,  30,  1910. 
Smith:  The  Mussel  Fishery  and  Pearl-button  Industry  of  the  Mississippi 

River.     Bui.  U.  S.  Fish  Com.,  1898. 

YOLDIA  LIMATULA. 

This  form  belongs  to  the  order  Protobranchia,  and  is  supposed 
to  be  one  of  the  most  primitive  of  living  lamellibranchs.  It 
lives  in  soft  mud,  such  as  is  found  in  quiet  coves  and  bays. 
(It  is  abundant  in  the  Eel  Pond  at  Woods  Holl.)  Although  it 
burrows  in  the  mud,  it  lives  near  the  surface,  and  frequently 
has  the  posterior  end  above  the  mud. 

1.  Place  a  specimen  in  a  dish  of  sea- water,  and  notice  the 
movements  and  shape  of  the  foot.  See  if  the  movements  are 


108 


MOLLUSCA. 


always  alike.  What  would  happen  if  such  movements  were 
made  by  a  specimen  lying  on  soft  mud?  Place  a  specimen  on 
mud  and  watch  the  results. 

2.  Leave  a  specimen  in  an  aquarium  in  which  two  inches  of 
bottom  mud  has  been  placed,  and  see  if  it  is  feeding  in  the  morn- 
ing. 

3.  Place  a  young,  transparent  specimen  in  a  watch-glass  of 
sea-water  and  study  the  parts.    The  foot  has  already  been 
observed.     Its  motions  will  probably  be  seen  again  here.     It 
has  been  considered  a  creeping  organ.     Do  you  find  evidence 
that  confirms  or  opposes  the  view?    With  a  low  power  of  the 
microscope  notice: 

4.  The  palps.    These  are  very  large.    The  outer  palp  on 
each  side  is  provided  with  a  long  appendage  that  may  be  pro- 
truded from  between  the  valves  of  the  shell.    This  is  the  feeding 
appendage. 

5.  The  gills.    These  are  quite  small  and  are  composed  of 
parallel  plates  that  are  capable  of  being  moved.    They  are 
situated  behind  the  palps,  are  attached  dorsally  by  muscular 
membranes  to  the  body- wall,  and  posteriorly  to  the  wall  that 
separates  the  siphons.    They  illustrate  what  is  supposed  to  be  the 
most  primitive  type  of  lamellibranch  gill.     Watch  their  move- 
ments and  see  if  you  can  determine  how  they  cause  the  jets  of 
water  to  leave  the  cloacal  siphon.     What  reason  is  there  for 
forming  such  strong  jets  of  water? 

6.  The  heart  and  ganglia  are  nicely  shown  in  such  a  speci- 
men. 

7.  Remove  one  of  the  shell  valves  of  an  adult  specimen  and 
examine  the  organs.    An  elongated  sense  tentacle  occurs  on  one 
or  the  other  side  of  the  base  of  the  branchial  siphon,  between  the 
wall  of  the  siphon  and  the  corresponding  mantle  lobe. 

A  drawing  of  the  organs  will  prove  profitable. 

Drew:  The  Anatomy,  Habits,  and  Embryology  of  Yoldia  limatula.     Mem. 

Biol.  Lab.  Johns  Hopkins  Univ.,  4,  1899. 
:  The  Life-History  of  Nucula  delphinodonta.     Quart.  Jour.  Mic.  Sci., 

44,  1901. 
Mitsukuri:  On  the  Structure  and  Significance  of  some  Aberrant  Forms  of 

Lamellibranchiate  Gills.    Quart.  Jour.  Mic.  Sci.,  21,  1881. 


V, 

MYTILUS   OR   MODIOLA.  109 


MYTILUS  OR  MODIOLA.    (Mussels.) 

These  animals  belong  to  the  order  Filibranchia,  and  show 
comparatively  simple  gills,  as  well  as  interesting  modifications 
for  their  manner  of  living.  They  live  attached  to  stones,  shells, 
piles,  or  even  to  sand  grains,  sometimes  in  moderately  deep 
water,  but  frequently  between  low-  and  high-tide  marks.  The 
two  forms  may  easily  be  distinguished  by  the  positions  of  their 
beaks.  The  beaks  of  Mytilus  form  the  anterior  end  of  the  shell. 
Those  of  Modiola  are  placed  a  short  distance  posteriorly.  You 
should  visit  "mussel  beds/'  and  see  where  and  how  they  are 
attached  and  on  what  they  must  depend  for  food. 

1.  Place  young  specimens  in  dishes  of  sea- water  and  see  if 
they  will  attach  themselves  by  their  byssal  threads.     (They  will 
generally  require  some  hours.)     If  you  can  get  them  to  attach 
to  slides,  the  attachment  may  be  microscopically  examined. 

2.  Test  the  strength  of  the  byssal  threads  of  a  rather  old 
specimen.    Are  they  elastic?    How  would  elasticity   aid  the 
animal  in  remaining  attached? 

3.  Leave  specimens  in  sea-water  for  some  hours,  and  see  if 
they  change  their  positions. 

4.  Notice  the  margins  of  the  mantle.    Are  they  fused?    Why 
are  siphons  not  necessary?    See  if  you  can  find  where  water 
passes  in  and  out. 

5.  Wedge  the  valves  of  a  specimen  apart,  cut  the  adductor 
muscles  (take  note  of  their  relative  size),  and  examine  the  ar- 
rangement of  organs. 

6.  Find  where  the  byssal  threads  are  attached. 

7.  Notice  the  relatively  small  foot,  and  compare  it  with  the 
powerful  foot  muscles.    Why  are  such  powerful  foot  muscles 
necessary  ? 

8.  See  how  the  gills  are  attached  to  the  body.    The  filaments 
of  the  gills  of  this  form  are  very  loosely  attached  to  each  other  by 
modified   clumps  of  cilia,   that  represent  the  inter-filamentar 
junctions.    Cut  off  a  piece  of  a  gill,  mount  it  in  sea-water  under 
a  cover,  and  examine  with  low  and  high  powers.     Find  places 
where  filaments  are  attached  by  the  bunches  of  cilia.    Find 


110  MOLLUSCA. 

places  where  the  cilia  have  pulled  apart.    Notice  the  size  and 
shape  of  the  ostia  and  find  the  two  kinds  of  movable  cilia. 

9.  This  form  usually  shows  the  way  food  is  gathered  espe- 
cially well.    Place  powdered  carmine  on  the  surface  of  a  gill  and 
see  what  becomes  of  it. 

10.  Notice  the  thickened  condition  of  the  mantle.    The  gonads 
extend  into  them,  and  the  thickening  is  due  to  sexual  products. 

Drawings  of  the  arrangement  of  the  organs,  and  especially  of 
the  microscopic  structure  of  the  gill,  will  prove  profitable. 

Meisenheimer:    Entwicklungsgeschichte    von    Dreissensia    polymorpha. 
Zeit.  f.  Wiss.  Zool.,  69,  1900. 

PECTEN  IRRADIANS.    (Scallop.) 

This  species  belongs  in  the  order  Pseudo-lamellibranchia 
and  lives  on  muddy  or  sandy  bottoms,  generally  where  the  water 
is  from  a  few  inches  to  several  fathoms  deep.  It  has  the  power 
of  swimming  pretty  well  developed.  At  rest  on  the  bottom  it 
always  lies  on  the  right  valve  of  the  shell. 

1.  Do  the  valves  of  the  shell  differ  in  color  or  shape? 

2.  On  each  side  of  the  beak  of  each  valve  is  a  flattened  pro- 
jection frequently  called  an  "ear"  or  "wing,"  the  posterior 
of  which  slopes  backward,  while  the  anterior,  especially  the  one 
on  the  right  valve,  is  somewhat  separated  from  the  body  of  the 
shell  by  a  notch. 

Place  specimens  in  dishes  of  sea-water,  and  when  they  have 
opened  their  shells  notice: 

3.  The  bright  specks,  the  pallial  eyes,  along  the  margins  of 
the  mantle.     Are  they  placed  in  any  order? 

4.  The  arrangement  of  the  tentacles  on  the  margins  of  the 
mantle.     Why  should  sense  organs  be  placed  in  this  position? 

5.  The  mantle  and  see  if  it  is  sensitive.     How  far  can  it  be 
drawn  back  into  the  shell?    What  muscles  are  used  in  with- 
drawing it?    Why  is  it  necessary  to  withdraw  it? 

6.  Specimens  in  aquaria  will  often  swim.     If  possible,  notice 
how  this  is  accomplished. 

Wedge  the  valves  of  a  specimen  apart  and  notice  the  single 
large  adductor  muscle.  What  need  has  Pecten  for  such  a  large 


OSTRBA   VIRGINIANA.  Ill 

adductor?  Notice  the  foot  and  compare  it  with  the  foot  of 
Venus. 

How  are  the  gills  attached  to  the  body?  What  would  be 
the  effect  on  the  gills  if  they  were  attached  to  the  mantle  and  to 
each  other,  as  in  most  forms,  when  water  is  ejected  in  swimming. 

Examine  the  structure  of  the  gill  and  notice  how  much 
larger  the  inter-filamentar  junctions  are  near  the  inter-lamellar 
junctions  than  elsewhere.  Near  the  margins  of  the  gills  the 
junctions  are  frequently  simple  bunches  of  cilia,  as  in  Mytilus. 
Observe  the  muscular  movements  of  the  gills.  The  gills  of  this 
form  need  to  be  muscular  so  they  can  be  drawn  together  when 
the  animal  swims. 

Drawings  to  show  the  arrangement  of  the  organs  and  the  struc- 
ture of  the  gill  are  desirable. 

Belding:  The  Scallop  Fishery  of  Massachusetts.    Mass.  Fish  and  Game 

Com.,  1910. 
Drew:  The  Habits,  Anatomy,  and  Embryology  of  the  Giant  Scallop,  Pecten 

tenuicostatus.     Univ.  of  Maine  Stud.,  No.  6,  1906. 

OSTREA  VIRGINIANA.    (Oyster.) 

This  also  belongs  to  the  order  Pseudo-lamellibranchia.  It 
forms  a  good  example  of  adaptations  for  a  sedentary  life.  It 
occurs,  fastened  to  rocks  and  other  shells,  in  positions  where  it  is 
much  exposed  to  attacks  of  the  enemies  of  lamellibranchs. 

1.  Notice  the  difference  in  the  size  and  shape  of  the  valves. 
Why  is  this  desirable? 

2.  Notice  the  thickness  of  the  valves  and  the  completeness 
with  which  they  come   in   contact  when  the   shell   is  closed. 
Would  such  a  heavy  or  tight-closing  shell  be  satisfactory  for  the 
scallop  or  the  razor-shell  clam? 

3.  Open  the  shell  by  breaking  the  edge,  inserting  a  knife- 
blade  through  the  opening,  and  cutting  the  adductor  muscle 
away  from  the  flattened  left  valve  of  the  shell  and  notice  the 
single  adductor,  extensive  gills,  and  the  absence  of  a  foot. 

Brooks:  The  Oyster. 

Grave:  Maryland  Shell-Fish  Commission,  4,  Rep.,  1912. 
Horst:  On  the  Development  of  The  European  Oyster  (Ostrea  edulus,  L.). 
Quart.  Jour.  Mic,  Sci.,  22,  1882, 


112  MOLLUSCA. 


SOLENOMYA. 

This  form*  a  member  of  the  order  Protobranchia,  with  much 
the  same  structure  as  Yoldia,  shows  an  interesting  method  of 
swimming  that  should  be  compared  with  Pecten,  and  with  the 
jets  of  water  formed  by  Mya.  Specimens  may  be  dug  at  low 
tide  from  mud  or  sandy  mud,  placed  in  a  dish  of  sea-water, 
and  observed.  Does  the  posterior  opening  in  the  mantle  cham- 
ber correspond  to  typical  siphons?  See  if  you  can  find  how  the 
animal  swims.  Is  the  movement  continuous  or  jerky?  Does  the 
animal  move  forward  or  backward?  Is  the  foot  active?  Are 
jets  of  water  thrown  from  the  shell?  Is  the  animal  adapted  to 
forming  jets  of  water? 

Examine  a  specimen  that  has  the  valves  closely  drawn  to- 
gether and  see  how  rounded  the  margins  appear.  Examine  a 
shell  from  which  the  animal  has  been  removed  by  maceration  and 
see  the  relation  of  the  shell  cuticle  and  the  calcareous  portion  of 
the  shell.  What  becomes  of  the  marginal  cuticle  when  the  shell 
is  closed?  Can  this  have  anything  to  do  with  throwing  jets  of 
water  from  the  shell  ? 

Drew:  Locomotion  in  Solenomya  and  its  Relatives.     Anat.  Anz.,  17,  1900. 
Stempell:  Zur  Anatomic  von  Solemya  togata.     Zool.  Jahrb.,  13,  1899. 


MYAARENAK1A.    (Long  Clam.) 

This  animal  belongs  to  the  order  Eulamellibranchia,  as  does 
Venus,  and  is  introduced  because  of  adaptations  for  its  manner 
of  living.  It  lives  buried  in  the  mud,  in  which  as  an  adult  it 
remains  stationary.  You  should  find  a  "clam  bed"  along  the 
shore,  and  after  noticing  the  pits  in  the  surface  of  the  mud,  and 
the  jets  of  water  that  are  sometimes  thrown  from  the  pits,  dig 
down  and  see  how  the  animals  are  placed.  If  the  water  is  calm, 
see  if  you  cannot  find  the  openings  of  the  siphons  at  the  surface 
of  the  mud,  of  specimens  that  are  still  covered  by  water.  You 
will  need  to  walk  very  carefully  so  as  to  disturb  mud  and  water 
as  little  as  possible,  as  the  siphons  are  otherwise  closed  and 
withdrawn. 


ENSIS   DIRECTUS.  113 

1.  Why  does  this  animal  not  need  a  shell  that  is  as  heavy 
and  closes  as  tightly  as  that  of  Venus  f    Does  it  show  the  same 
points  regarding  the  valves  (umbos,  beaks,  lines  of  growth,  and 
ligament)?    Later,  when  the  shell  is  removed,  the  large  carti- 
lage pit  on  the  left  valve  will  be  seen. 

2.  The  ventral  borders  of  the  mantle  lobes  are  united  except 
near  the  anterior  end,  where  there  is  a  space  through  which  the 
foot  may  be  seen. 

3.  The  siphons  are  large  and  muscular  and  may  be  retracted, 
as  in  the  specimen  that  you  are  handling,  or  may  be  greatly 
extended,  as  may  sometimes  be  seen  in  aquarium  specimens. 
Why  does  Mya  need  larger  siphons  than  Venus  does  ? 

4.  Pick  up  a  specimen  that  has  the  siphons  extended  and 
notice  the  powerful  ejection  of  water.     Is  it  ejected  from  one 
or  both  openings?    How  is  this  accomplished?    Of  what  service 
can  such  jets  be  to  the  animal  ?    Why  are  powerful  jets  of  this 
nature  of  more  service  to  Mya  than  to  Venus? 

Notice  the  cartilage  in  the  cartilage  pit  on  the  left  valve. 
What  function  does  it  perform?  Why  is  there  no  need  for  a 
large  and  powerful  foot?  It  is  much  easier  to  trace  the  alimen- 
tary canal  and  the  ganglion  connectives  in  this  form  than  in  Ve- 
nus f 

Belding:  The  Mollusk  Fisheries  of  Massachusetts.     Mass.  Fish  and  Game 

Com.,  1909. 
Kellogg:  Life-History  of  the  Common  Clam,  Mya  arenaria.     Bui.  U.  S. 

Fish  Com.,  1899. 
Mead  and  Barnes:  Observations  on  the  Soft-shell  Clam.     Rhode  Island 

Com.  Inland  Fish.,  20  to  24,  1900  to  1904. 

ENSIS  DIRECTUS.    (Razor-shell  Clam.) 

This  species  is  another  representative  of  the  order  Eulamel- 
libranchia  and  is  introduced  because  of  its  adaptation  for  a 
burrowing  habit,  and  because  of  the  great  ease  with  which  its 
nervous  system  can  be  studied.  Individuals  are  not  uncommon 
on  mud-  or  sand-flats  from  which  the  water  flows  at  low  tide. 
They  may  sometimes  be  seen  protruding  above  the  surface  of 
the  mud,  but  are  hard  to  approach  because  of  their  great  sen- 
8 


114  MOLLUSCA. 

sitiveness.    Upon  being  disturbed  they  quickly  disappear  be- 
neath the  surface  of  the  mud. 

1.  Notice  the  shape  of  the  shell,  the  way  it  gapes  at  both 
ends,  and  the  way  the  lobes  of  the  mantle  are  fused. 

2.  With  a  pencil-point  or  seeker  stroke  the  tentacles  around 
the  siphon  openings,  while  the  animal  is  being  held  anterior  end 
downward.     This  will  cause  it  to  perform  the  burrowing  move- 
ments.   Study  the  movements  carefully  and  see  what  the  effects 
would  be  were  they  performed  in  mud.   Thrust  the  anterior  end 
of  the  shell  in  mud  and  watch  the  result  of  the  movements. 

3.  Water  is  ejected  by  the  sides  of  the  foot  to  aid  in  burrow- 
ing or  to  enable  the  animal  to  swim,  but  observations  on  its 
method  of  ejecting  it  are  not  easily  made,  and  are  sure  to  take 
much  time.     Notice  the  way  the  anterior  margins  of  the  lobes 
of  the  mantle  scrape  mud  from  the  foot  when  the  foot  is  being 
withdrawn. 

4.  With  a  scalpel  separate  the  united  margins  of  the  mantle 
throughout  their  length.     Slowly  pry  the  valves  apart,  lift  up 
the  free  end  of  the  foot  and  pull  it  posteriorly. 

The  cerebral  ganglia  are  plainly  visible  without  further  cutting. 
They  lie  just  posterior  to  the  anterior  adductor  muscle  and  in  front 
of  the  mouth,  and  are  widely  separated.  They  are  connected  by 
a  narrow  commissure,  and  each  gives  rise  to  a  cerebro-visceral 
and  a  cerebro-pedal  connective  and  to  a  number  of  nerves.  The 
nerves  that  supply  the  anterior  part  of  the  mantle  and  the  ante- 
rior adductor  muscle  are  especially  easily  seen. 

5.  If  the  specimen  is  one  that  is  nearly  or  quite  dead,  it  is, 
by  cutting,  easy  to  follow  the  cerebro-pedal  connectives  to  the 
pedal  ganglia,  which  are  not  far  from  the  base  of  the  foot  and 
not  deeply  embedded. 

6.  Allow  the  foot  to  return  to  its  normal  position  and  cut 
along  the  line  of  union  of  the  inner  gills.     Without  further  cut- 
ting the  visceral  ganglia  may  be  studied.     Their  connectives, 
which  may  be  followed  easily  as  far  forward  as  the  palps,  and 
the  posterior  pallial  and  the  branchial  nerves  may  be  seen. 

A  drawing  of  the  nervous  system  should  be  made. 


CH^TOPLEURA.  115 

Drew:  The  Habits  and  Movements  of  the  Razor-shell  Clam,  Ensis  direc- 

tus.     Biol.  Bui.,  12,  1907. 
:  The  Physiology  of  the  Nervous  System  of  the  Razor-shell  Clam, 

Ensis  directus.     Jour.  Exp.  Zool.,  5,  1908. 


AMPHINEURA. 

CHAETOPLEURA. 

It  will  be  profitable  to  study  only  external  features,  unless 
time  is  to  be  had  for  cutting  and  studying  sections,  as  the  species 
is  small  and  difficult  to  dissect.  Its  apparently  generalized  struc- 
ture, and  its  adaptations,  make  it  desirable  for  students  to  under- 
stand from  descriptions  and  figures  the  main  features  of  its  an- 
atomy. 

1.  Examine  specimens  that  are  attached  to  stones  and  shells 
and  see  how  nicely  they  adapt  their  shapes  to  the  shapes  of  the 
objects  to  which  they  are  attached.     How  is  this  possible? 

2.  Remove  a  specimen  and  quickly  transfer  it  to  a  clean 
glass  slide,  applying  its  ventral  side  to  the  glass.     Put  your 
finger  in  its  back  and  prevent  it  from  curling  for  a  minute.     It 
will  then  generally  remain  attached  to  the  slide  and  may  be 
studied  from  both  sides. 

3.  How  many  plates  are  there?    What  is  the  shape  of  each? 
Do  they  apparently  join  edge  to  edge  or  do  they  overlap?    Do 
the  plates  extend  clear  to  the  margin  of  the  animal?    What 
reason  is  there  for  having  plates  instead  of  a  solid  dorsal  shell  ? 

4.  Notice  the  thickened  margin  of  the  animal,  and  see  that 
dorsally  it  bears  spicules,  while  ventrally  it  is  smooth  and  is 
applied  closely  to  the  slide. 

5.  Notice  the  flattened  elliptical  foot.    Do  you  understand 
how  the  animal  creeps  and  adheres? 

6.  In  front  of  the  foot  is  the  head  fold  in  which  the  mouth  can 
be  seen. 

7.  In  the  furrow  bordering  the  foot  are  the  gills. 

8.  Remove  the  animal  from  the  slide  and  see  how  it  curls  up, 
Try  to  unroll  it. 


116  MOLLUSC  A. 

9.  If  you  care  to  see  the  radula,  the  organ  that  especially 
indicates  affinity  to  the  Gastropoda,  it  can  be  pulled  out  by  grasp- 
ing just  behind  the  mouth  with  pointed  forceps  and  pulling 
forward.  When  removed  it  may  be  mounted  on  a  slide  with 
water  and  studied  with  the  microscope. 

Haller:  Die  Organisation  der  Chitonen  der  Adria.  Arb.  Zool.  Inst.  Wien., 

4,  1882;  5,  1884. 
Heath:  The  Development  of  Ischnochiton.    ZooL  Jahrb.,  12  (Anat.),  1899. 


GASTROPODA. 

A  majority  of  the  Gastropoda  have  the  body  protected  by  a 
spirally  wound  shell,  and  crawl  around  by  means  of  a  flattened 
muscular  foot  that  forms  the  ventral  portion  of  the  body. 

Examine  specimens  of  Tritia  or  any  other  active  form 
and  notice: 

1.  The  relation  of  the  animal  to  its  shell  when  retracted  and 
when  extended. 

2.  Movements.     Can  you  determine  how  are  they  performed? 

3.  The  movements  of  the  tentacles  and  proboscis.    What  do 
the  movements  accomplish? 

4.  Touch  a  specimen  and  see  what  positions  the  parts  take 
when  it  retracts  into  the  shell.     If  the  animal  has  an  operculum 
see  where  it  is  borne  and  how  it  fits  into  the  aperture  of  the 
shell. 

FULGUR  (SYCOTYPUS). 

This  large  gastropod  lives  in  comparatively  shallow  water 
and  depends  largely  on  other  Mollusca  for  its  food.  Examine 
a  retracted  specimen  and  see  how  the  shell  is  closed  by  a  horny 
lid,  the  operculum.  Examine  expanded  specimens  in  the  aqua- 
ria, and  see  where  the  operculum  is  placed.  What  position 
must  the  animal  assume  in  the  shell  to  bring  the  operculum  in 
position? 

Shell. — A  somewhat  conical  tube,  spirally  wound,  somewhat 
like  a  spiral  stairway.  Observe  the  following  parts: 


FULGUR    (SYCOTYPUS).  117 

1.  The  apex,  forming  the  closed  end  of  the  tube. 

2.  The  spire.    How  many  whorls  are  there?    Do  they  differ 
in  number  in  different  specimens?     In  what  direction  are  the 
whorls  wound?     (Hold  the  apex  toward  you  in  determining 
this  point.)     Examine  old  and  young  specimens  and  see  if  there 
is  evidence  that  the  apex  is  worn  off. 

3.  The  body-whorl.    The  one  that  opens  to  the  outside. 

4.  The  columella.    The  axis  around  which  the  whorls  are 
wound.    This  is  best  studied  in  a  broken  shell. 

5.  The  aperture,  which  is  bounded  by  the  inner  lip  on  the 
columellar  side  and  by  the  outer  lip  along  the  free  edge. 

6.  The  siphonal  canal,  which,  forms  the  spout-like  prolonga- 
tion of  the  shell. 

7.  The  lines  of  growth.    What  do  they  represent?    Do  they 
show  evidence  of  injuries  that  have  befallen  the  shell  during  the 
life  of  the  individual  ? 

8.  In  structure  the  shell  presents  three  layers.     In  a  broken 
shell  notice:  (a)  the  cuticle,  worn  away  from  the  greater  portion 
of  the  shell;    (b)  the  nacre,  smooth  and  lining  the  inner  surface 
of  shell;    (c)  the  middle  layer.     How  can  three  layers  be  secreted 
by  the  mantle  that  lines  one  of  them? 

Draw  two  figures,  one  of  a  perfect  and  one  of  a  broken  shell. 

9.  Compare  the  shell  with  the  shells  of  other  forms,  such  as 
Lunatia,  Bulla,  Haliotus,  Crepidula,  and  Acmsea. 

Soft  Parts. — Examine  an  animal  that  has  been  removed  from 
its  shell  and  killed  while  more  or  less  expanded 1  and  see  in  what 
position  it  was  placed  in  the  shell.  Compare  the  number  of 
whorls  made  by  it  to  the  number  in  the  shell.  Understand  which 
is  right  and  which  is  left  for  the  coiled  part  of  the  body.  Which 

1  This  can  be  accomplished  by  breaking  the  shell  away  with  the  blade 
of  a  hatchet,  and  when  enough  of  the  shell  has  been  removed,  loosening  the 
muscle  from  the  columella  with  the  thumb,  and  then  pulling  and  twisting 
the  animal  out.  When  free  from  the  shell  place  the  animal  in  sea-water 
to  which  has  been  added  about  one-tenth  its  volume  of  alcohol  and  a  little 
turpentine  (about  10  c.c.  of  turpentine  to  each  100  c.c.  of  alcohol)  and  leave 
for  several  hours.  An  animal  treated  in  this  way  will  usually  die  with  its 
proboscis  extended.  For  the  method  we  are  indebted  to  Mr.  Geo.  M. 
Gray,  Curator  at  the  Marine  Biological  Laboratory,  Woods  Holl,  Mass. 


118  MOLLUSCA. 

side  was  applied  to  the  columella?    In  determining  the  position 
of  organs,  constantly  keep  the  sides  in  mind. 

Before  beginning  the  dissection,  note  the  following  parts: 

1.  The  visceral  dome.     The  portion  that  extended  into  the 
spire  of  the  shell. 

2.  The  mantle,  which  is  thin  and  closely  applied  to  the  visce- 
ral dome,  and  raised  to  form  a  thickened  collar  that  extends 
entirely  around  the  body  along  a  line  that  corresponds  to  the 
aperture  of  the  shell. 

3.  The  siphon,  which  is  a  spout-like  prolongation  of  the  col- 
lar.    Into  what  portion  of  the  shell  does  it  fit  ? 

4.  The  mantle  chamber.    This  can  be  seen  by  raising  the  edge 
of  the  collar  of  the  mantle. 

5.  The  head,  which  forms  an  anterior  prolongation. 

6.  The  tentacles,  forming  two  triangular  projections  on  the 
head. 

7.  The  eyes,  pigmented  spots  on  the  outer  edges  of  the  ten- 
tacles. 

8.  The   proboscis,   which,   when  extended,   protrudes   from 
beneath  the  portion  that  bears  the  tentacles.     What  is  its  size, 
shape,  and  general  appearance?    It  may  be  retracted  entirely 
into  the  body. 

9.  The  mouth,  at  the  end  of  the  proboscis.     The  end  of  the 
odontophore  may  frequently  be  seen  protruding  from  the  mouth. 

10.  The  foot.     What  is  its  position,  consistency,  color,  and 
shape  ? 

11.  The  opening  of  the  pedal  gland,  on  the  sole  of  the  foot. 
Is  the  pedal  gland  well  developed  in  both  sexes?    Do  you  know 
its  function? 

12.  The  operculum.     Notice  its  position  and  attachment. 

13.  If  the  specimen  is  a  male,  the  large,  somewhat  flattened 
and  bent  penis,  a  little  to  the  right  and  posterior  to  the  right  ten- 
tacle. 

A  number  of  organs  may  be  seen  through  the  somewhat 
transparent  mantle.     These  are: 

14.  The  liver,  which  forms  the  first  two  whorls  of  the  spire. 
Notice  its  color. 


FULGUR    (SYCOTYPUS).  119 

15.  The  gonad,  which  is  borne  on  the  dorsal  surface  of  the 
liver,  and  differs  in  individuals  from  red  and  brown  to  yellow. 

16.  The  stomachy  which  lies  on  the  left  (external)  surface  of 
the  liver.     It  is  curved  and  light  colored  and  is  frequently  rather 
indistinct. 

17.  The  kidney,  which  lies  on  the  dorsal  surface,  and  a  little 
to  the  left  side,  on  the  anterior  end  of  the  liver.     It  is  somewhat 
rectangular  in  shape  and  differs  in  color  from  a  yellowish-brown 
to  a  chocolate  color.    The  kidney  is  composed  of  two  parts, 
the  large  acinous  portion,  and  the  smaller  tubuliferous  portion. 
The  latter  lies  along  the  left  side  of  the  former,  by  the  side  of 
the  pericardium. 

18.  The  pericardium  lies  to  the  left  of  the  anterior  end  of 
the  kidney.     Through   its  dorsal  wall  the  yellowish  heart  can 
generally  be  seen. 

19.  The  columellar  muscle,  which  attaches  the  animal  to  its 
shell,  and  enables  it  to  withdraw,  can  be  traced  to  the  foot. 

20.  If  the  specimen  being  examined  is  a  female,  the  large 
yellowish  nidamental  gland  will  be  seen  near  the  right  side. 

21.  The  large,  brownish  gill  lies  to  the  left  of  the  nidamental 
gland  in  the  female  and  anterior  to  the  heart. 

22.  The  osphradium  is  a  small,  brownish  organ  to  the  left 
of  the  anterior  end  of  the  gill  and  at  the  base  of  the  siphon. 

23.  The  hypobranchial  gland  is  a  glandular  portion  of  the 
mantle,  to  the  right  of  the  gill  (between  the  gill  and  the  nida- 
mental gland,  in  the  female). 

Make  a  drawing  of  the  animal  as  a  whole,  showing  as  many 
of  the  observed  points  as  possible. 

Open  the  mantle  chamber  by  cutting  the  mantle  along  the 
right  side  of  the  gill  to  the  limit  of  the  cavity,  reflect  the  flaps, 
and  notice  the  position  and  structure  of  the  gill,  osphradium, 
hypobranchial  gland  (cut  in  opening  the  mantle  cavity),  and,  if 
the  specimen  is  a  female,  the  nidamental  gland.  The  open- 
ing of  the  rectum  will  be  seen  at  the  end  of  a  short  papilla 
in  the  right  side  of  the  mantle  cavity.  The  opening  of  the 
nidamental  gland  will  be  seen  on  an  elevation  a  little  to  the  right 


120  MOLLUSC  A. 

and  anterior  to  the  anus.  If  possible,  insert  a  guarded  bristle 
into  this  opening  and  see  what  becomes  of  it.  Trace  the  oviduct 
from  the  ovary  along  the  columellar  side  of  the  liver.  See  what 
becomes  of  it.  Examine  the  inside  of  the  nidamental  gland 
and  see  its  relation  to  the  oviduct. 

If  the  specimen  is  a  male,  follow  the  vas  deferens  from  the 
testis  to  the  base  of  the  penis. 

Circulatory  System. — Remove  the  thin  membrane  that  forms 
the  roof  of  the  pericardial  chamber. 

1.  The  heart  consists  of :  (a)  the  large,  rounded  ventricle; 
(b)  the  smaller,  conical,  thin-walled  auricle. 

2.  The  auricle  receives  blood  by  two  vessels.     One,  return- 
ing blood  from  the  gill,  runs  along  the  left  side  of  the  gill  to  its 
posterior  end,  where  it  bends  abruptly  to  the  right  along  the 
margin  of  the  pericardial  cavity,  and  enters  the  auricle.    The 
other  returns  blood  from  the  tubuliferous  portion  of  the  kidney 
and  follows  the  right  side  of  the  pericardium  to  the  auricle. 

3.  The  gill  receives  its  blood  through  a  vessel  that  borders 
its  right  side.    This  vessel  receives  the  blood  from  a  portion  of 
the  mantle,  and  from  the  large,  acinous  portion  of  the  kidney. 

4.  The  blood  leaves  the  ventricle  by  a  single  vessel,  the  aorta, 
that  almost  immediately  gives  rise  to  the  visceral  artery  which 
supplies  the  visceral  hump.    Trace  its  distribution. 

The  aorta  makes  an  abrupt  turn  downward  and  forward  and 
enlarges  to  form  the  secondary  heart  which  lies  alongside  the  eso- 
phagus. Follow  the  course  of  the  aorta  and  its  branches. 

The  course  of  general  circulation  is,  beginning  with  the  heart, 
(a)  system,  (b)  kidney,  (c)  gill,  and  (d)  back  again  to  the 
heart.  Why  is  such  a  course  of  circulation  better  than  the 


reverse 


Draw  a  figure  showing  the  vascular  system. 

Excretory  System. — The  two  portions  of  the  kidney  have 
already  been  noticed.  Cut  along  their  common  line  of  union 
and  examine  the  inner  surface  of  each  part. 

1.  Notice  the  parallel  lines  of  tubules  that  form  the  substance 
of  the  tubuliferous  portion,  and  the  lobules  that  form  the  com- 
paratively thick  walls  of  the  acinous  portion. 


FULGUR    (SYCOTYPUS).  121 

2.  Find  the  slit-like  opening  that  leads  from  the  kidney  to 
the  mantle  cavity.  It  is  at  a  point  between  the  two  portions  of 
the  kidney  and  is  easily  found  from  the  mantle  chamber.  A 
small  opening  leads  into  the  pericardium,  but  it  is  hard  to  find 
it  in  dissections. 

Digestive  System. — 1.  Remove  part  of  the  integument  at  the 
base  of  the  proboscis  and  find  the  muscles  that  retract  it.  How 
many  are  there  and  how  are  they  attached  ?  Do  you  understand 
how  the  proboscis  is  extended? 

2.  With  a  pair  of  scissors  open  the  extended  proboscis  along 
the  ventral  line,  pin  it  open,  and  notice  that  the  exposed  muscu- 
lar mass,  the  buccal  mass,  is  attached  to  the  wall  of  the  proboscis 
in  the  region  of  the  mouth,  at  its  base,  and  by  means  of  fibers, 
along  its  sides. 

3.  Push  the  muscular  mass  slightly  to  one  side  and  notice 
the  esophagus,  which  is  closely  applied  to  the  dorsal  wall  of  the 
proboscis.     Notice  the  muscle  fibers  that  extend  from  it  to  the 
proboscis.    What  is  their  function? 

4.  The  odontophoral  apparatus  consists  of  a  forked  cartilage, 
the  odontophoral  cartilage,  that  is  surrounded  by  muscles  and 
cannot  be  seen  until  these  are  removed,  a  radula  which  is  for 
most  of  its  length  enclosed  in  a  sac,  the  radular  sac,  and  is  ex- 
posed only  in  the  region  of  the  mouth,  and  the  muscles  for  mov- 
ing the  cartilage  and  the  radula. 

(a)  The  strands  of  muscles  that  run  from  its  sides  forward 
to  be  inserted  on  the  walls  of  the  proboscis  are  attached  to  a 
cartilage,  the  odontophoral  cartilage.  These  are  the  cartilage 
protractors. 

(6)  Attached  to  the  ends  of  the  two  horns  of  the  cartilage 
and  running  posteriorly  to  be  attached  to  the  walls  of  the  pro- 
boscis near  its  base  are  the  flat  cartilage  retractors. 

(c)  Running  lengthwise  of  the  buccal  mass,  on  its  ventral 
side,  are  three  pairs  of  slender  muscles,  one  pair  median  and  the 
others  covering  the  horns  of  the  odontophoral  cartilage  that  has 
just  been  observed.  Find  to  what  the  muscles  are  attached 
anteriorly  and  posteriorly.  If  the  animal  is  fresh,  pull  on  them 


122  MOLLUSCA. 

with  the  forceps  and  see  what  moves.    These  are  the  radula 
protractors. 

(d)  Beneath  the  radula  protractors  observe  the  sheet  of  cross- 
fibers  that  bind  the  horns  of  the  odontophoral  cartilage  together. 

Make  a  drawing  showing  the  ventral  side  of  the  buccal  mass. 

(e)  A  portion  of  the  radula  is  visible  near  the  anterior  end  of 
the  proboscis.     Introduce  a  bristle  into  the  esophagus  and  deter- 
mine its  relation  to  the  exposed  radula. 

(/)  Loosen  the  anterior  end  of  the  buccal  mass  from  the  wall 
of  the  proboscis,  turn  it  back  and  see  how  the  radula  passes 
around  the  odontophoral  cartilage.  With  a  hand-lens  notice 
the  teeth  on  the  open  radula,  ventral  to  the  cartilage,  and  see 
how  the  radula  is  folded  as  it  passes  over  the  dorsal  side  of  the 
cartilage  so  the  teeth  are  turned  in.  What  reason  is  there  for 
folding  the  radula  in  this  manner? 

(g)  Cut  the  cartilage  protractors  and  reflect  the  buccal  mass. 
It  is  attached  to  the  wall  of  the  proboscis  at  its  posterior  end  by 
strong  muscles,  the  radula  retractors.  These  may  be  studied 
after  cutting  the  sheath  of  cross-fibers  that  hold  the  mass  to- 
gether. Determine  how  they  are  attached  to  the  sides  of  the 
radula.  Why  do  they  need  to  be  so  powerful? 

Make  a  drawing  of  the  buccal  mass  as  seen  from  the  dorsal  side. 

(h)  Pull  away  the  muscles  and  examine  the  shape  of  the 
odontophoral  cartilage  and  its  relation  to  the  radula. 

(i)  Remove  the  radula,  unfold  it,  and  examine  it  microscop- 
ically. Do  the  teeth  differ  in  any  way  at  the  two  ends?  Why 
is  the  radula  so  long? 

Draw  a  portion. 

The  radula  is  the  organ  upon  which  most  gastropods  depend 
for  getting  food.  You  should  understand  how: 

1.  The  proboscis  is  protruded  and  retracted. 

2.  The  odontophoral  cartilage  is  protruded  and  retracted. 

3.  The  radula  is  protracted  and  retracted. 

4.  The  radula  is  folded  by  the  cartilage  and  spread  for  action. 

5.  The  food  is  torn  off  and  taken  into  the  mouth. 

Near  the  base  of  the  proboscis  is  a  pair  of  large,  yellow 


FULGUB    (SYCOTYPUS).  123 

salivary  glands,  the  ducts  from  which  extend  on  either  side  of 
the  esophagus  to  the  mouth.  Further  back,  on  the  right  side 
of  the  esophagus,  is  the  delicate  pancreas. 

Trace  the  esophagus  to  the  stomach  and  the  intestine  to  the 
anus. 

Nervous  System. — Most  of  the  ganglia  are  grouped  around  the 
esophagus,  about  three-quarters  of  an  inch  posterior  to  the  base 
of  the  proboscis.  They  are  all  brown  and  accordingly  conspic- 
uous. Cut  around  its  base  so  the  proboscis  may  be  turned  back, 
and  the  ganglia  on  the  ventral  surface  of  the  esophagus  may  be 
seen.  Carefully  pick  away  the  tissue  that  covers  the  ganglia  and 
notice  on  the  ventral  side  of  the  esophagus: 

1.  The   small   but   conspicuous   buccal  ganglia.     These   are 
united  with  each  other  and  with  the  cerebral  ganglia  and  send 
nerves  to  the  mouth  apparatus. 

2.  The  large  pedal  ganglia,  fused   together  but   distinctly 
paired,  lying  posterior  to  the  buccal  ganglia  and  sending  nerves 
to  the  two  sides  of  the  foot.    Each  is  united  by  connectives  with 
the  corresponding  cerebral  and  pleural  ganglia. 

From  the  dorsal  side  a  number  of  ganglia  may  be  seen,  more 
of  which  lie  to  the  right  than  to  the  left  of  the  median  line. 

1.  On  the  left  side  there  are  two  ganglia  that  are  in  rather 
close  union  with  each  other.     The  most  anterior,  the  left  cerebral, 
is  the  larger  of  the  two.     The  left  pleural  joins  it  posteriorly  and 
ventrally  and  extends  nearly  to  the  ventral  side  of  the  esophagus. 

2.  On  the  right  side  four  ganglia  may  be  distinguished.     The 
right  cerebral  and  right  pleural  are  fused  to  form  one  mass,  but 
there  is  a  marked  constriction  between  them.     Posteriorly  and 
dorsally  the  right  pleural  is  connected  by  a  connective  with  the 
right  visceral,  which  lies  very  close  to  it.     The  remaining  ganglion, 
the  left  visceral,  which  is  almost  in  contact  with  the  right  pleural 
and  right  pedal  ganglia,  lies  ventrally  and  to  the  right  of  the 
right  visceral  ganglion.     It  is  connected  with  the  left  pleural 
ganglion  by  a  connective  that  runs  behind  the  pedal  ganglia. 
There  seems  also  to  be  a  connection  with  the  right  pleural  gan- 
glion, but  this  must  be  considered  a  secondary  connection.     Do 
you  understand  why  this  ganglion  occupies  this  position? 


124  MOLLUSCA. 

3.  Another  ganglionic  mass,  the  abdominal  ganglion,  possi- 
bly formed  by  the  fusion  of  two  ganglia,  lies  just  below  the  exter- 
nal opening  of  the  kidney,  where  it  can  be  seen  as  a  brown  mass, 
through  the  body-wall.  It  lies  on  the  elongated  commissure 
that  connects  the  two  visceral  ganglia.  The  commissure  may  be 
followed  by  dissection. 

The  cerebral  ganglia  are  the  most  centralized.  Besides  being 
connected  with  each  other  by  a  commissure  dorsal  to  the  esopha- 
gus, and  being  intimately  connected  with  the  pleural  ganglia, 
each  cerebral  ganglion  is  connected  with  the  corresponding  buc- 
cal  and  pedal  ganglion,  and,  through  the  pleural,  with  the  visceral 
ganglion.  The  visceral  ganglia  are  connected  with  each  other 
by  a  long  commissure  on  which  the  abdominal  ganglion  is  placed. 
Each  pedal  ganglion  receives  connectives  from  the  cerebral  and 
from  the  pleural  ganglion  of  the  corresponding  side. 

Draw  figures  of  the  nervous  system  and  compare  thefti  with 
the  clay  model.1 

Colton:  How  Fulgur  and  Sycotypus  Eat  Oysters,  Mussels,  and  Clams. 
Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1908. 

Conklin:  The  Embryology  of  Fulgur:  A  Study  of  the  Influence  of  Yolk  on 
Development.  Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1907. 

:  The  Embryology  of  Crepidula.     Jour.  Morph.,  13,  1897. 

Glaser:  tJber  den  Kannibalismus  bei  Fasciolaria  tulipa  (var.  distans)  und 
deren  larvale  Excretionsorgane.  Zeit.  f.  wiss.  Zool.,  80,  1905. 

Herrick :  Mechanism  of  the  Odontophoral  Apparatus  in  Sycotypus  canalicu- 
latus.  Am.  Nat.,  40,  1906. 

Orton:  An  Account  of  the  Natural  History  of  the  Slipper-Limpet  (Crepi- 
dula fornicata).  Jour.  Marine  Biol.  Ass.,  9,  1912. 

Patten:  The  Embryology  of  Patella.    Arb.  Zool.  Inst.  Wien.,  6,  1886. 


CEPHALOPODA. 
LOLIGO    PEALII.    (The  Squid.) 

Specimens  of  this  or  closely  related  species  are  rather  common 
along  the  Atlantic  coast  of  the  United  States.  They  are  active 
swimmers,  but  may  occasionally  be  seen  in  shallow,  quiet  water 
near  the  shore.  The  movements  and  positions  of  adult  speci- 

1  Instructors  will  find  that  a  model  prepared  by  sticking  lumps  and 
strands  of  modeling  clay  on  a  cylindrical  graduate,  to  illustrate  the  positions 
of  the  ganglia  and  connectives  on  the  esophagus,  will  greatly  aid  the 
students. 


LOLIGO   PEALII.  125 

mens  in  aquaria  should  be  studied.    Do  you  know  what  they 
eat  and  how  they  capture  their  food  ? 

Study  a  small  living  specimen  in  a  jar  of  sea- water  and  no- 
tice: 

1.  Its  general  shape  and  distinct  head. 

2.  Its  position  in  the  water.     For  convenience,  the  lower 
surface  may  be  referred  to  as  ventral,  but  this  is  not  to  be  con- 
sidered as  morphologically  the  same  as  the  ventral  surface  of 
other  Mollusca.     What  parts  are  kept  moving?    Why  is  water 
pumped  when  the  animal  is  not  swimming? 

3.  In  what  direction  it  can  swim  best.     Can  it  swim  in  the 
other  direction?    How  does  it  swim?    Is  the  funnel  movable? 
How  does  it  guide  its  movements? 

4.  Its  color.     Irritate  it  and  see  what  happens.     What  pur- 
pose does  the  change  in  color  serve?    What  is  the  ink  for? 

5.  What  happens  when  the  end  of  a  finger  is  placed  within 
the  circlet  of  tentacles  of  an  animal  about  two  inches  long  that 
is  being  held  firmly? 

Using  an  adult  specimen,  observe: 

6.  The  arrangement  of  the  arms  on  the  head.     Are  they  ar- 
ranged in  any  definite  order?    Are  they  all  alike? 

7.  The  suckers  of  the  arms.    Do  they  follow  the  same  order 
on  all  of  the  arms? 

8.  The  structure  of  a  sucker.    Notice  the  peduncle,  outer 
thin  margin,  horny  ring,  and  piston.     Is  the  horny  ring  smooth? 
What  is  its  function?    How  does  the  sucker  work?    Split  one 
and  draw  the  cut  surface. 

9.  The  mouth.    Where  is  it  placed?    Notice  the  tips  of  the 
horny  beak.     Which  jaw  is  longest? 

10.  The  eyes. 

11.  The  fold  of  tissue  behind  each  eye.    These  have  been 
called  the  olfactory  organs. 

12.  The  attachment  of  the  head  and  the  extent  of  the  mantle 
opening  around  the  neck. 

13.  The  funnel  protruding  from  beneath  the  mantle  on  the  ven- 
tral surface.     Notice  the  position  and  character  of  its  opening. 


126  MOLLUSCA. 

14.  The  median  dorsal  projection  of  the  mantle. 

15.  The  tail-fin,  its  position,  shape,  and  color.     What  is  its 
function? 

Draw  the  animal  as  seen  from  the  ventral  side. 

Carefully  open  your  specimen  by  cutting  through  the  mantle 
a  little  to  one  side  of  the  mid-ventral  line,  and  expose  the  man- 
tle chamber. 

Notice: 

1.  The  thickness  and  character  of  the  mantle  and  its  relation 
to  the  rest  of  the  body.     Why  does  it  need  to  be  so  muscular? 

2.  The  arrangement  of  the  funnel.     Why  does  it  have  a 
thin  posterior  edge?    How  is  it  held  in  position  against  the 
mantle?    Does  it  have  a  valve?    Is  the  funnel  movable  in  the 
living  animal? 

3.  The  free  edge  of  the  mantle  and  its  relation  to  the  folds 
beneath  the  eyes.     Do  you  understand  how  the  water  gets  into 
and  out  of  the  mantle  cavity? 

4.  The  large  retractor  muscles  of  the  funnel.    How  many  are 
there?    How  can  the  funnel  be  pointed  in  different  directions? 
What  need  is  there  for  such  a  provision? 

5.  The  retractor  muscles  of  the  head.    How  many  are  there? 
Are  they  used  in  swimming  in  any  way? 

6.  The  rectum,  opening  near  the  base  of  the  funnel  between 
two  small  lateral  flaps  of  tissue. 

7.  The  ink-bag,  dorsal  to  the  rectum  and  opening  into  it 
near  the  anus. 

8.  The  gills,  extending  from  a  point  about  midway  of  the 
body  toward  the  free  edge  of  the  mantle.     How  many  are  there  ? 
How  are  they  attached  ?    Why  does  an  animal  that  is  not  swim- 
ming continually  pump  water  through  the  mantle  chamber? 

9.  The  branchial  hearts,  at  the  bases  of  the  gills,  rounded, 
light  colored  organs  that  can  be  seen  through  the  membrane 
covering  them. 

10.  The  median  ventral  mesentery. 
If  the  specimen  is  a  male,  notice: 

1.  The  slender,  tapering  penis,  to  the  left  of  the  rectum. 


LOLIGO   PEALII.  127 

2.  The  kidneys,  white  organs  to  be  seen  through  the  mem- 
branous covering,  between  the  bases  of  the  gills.    From  this 
position  they  taper  anteriorly  for  half  an  inch  or  more  and  send 
small  lobes  posteriorly. 

3.  The  openings  of  the  kidneys  near  their  anterior  ends,  on 
small  papillae. 

4.  The  conical  posterior  portion  of  the  viscera.    This  is  com- 
posed of  a  large  visceral  sac  and  portions  of  the  sexual  organs. 

Draw  the  animal,  showing  the  points  observed. 
If  the  animal  is  a  female,  notice: 

1.  The  pair  of  large,  white  nidamental  glands  that  cover  a 
portion  of  the  rectum  and  the  greater  part  of  the  ink-bag. 

2.  The  openings  of  these  glands  at  their  anterior  ends.    Do 
you  know  the  function  of  these  glands  ? 

3.  The  opening  of  the  oviduct  dorsal  to,  and  a  little  to  the 
left  of,  the  left  nidamental  gland. 

4.  The  mass  of  eggs  that  fills  the  posterior  portion  of  the  body. 
These  are  in  the  ovary  and  oviduct. 

Draw  the  animal,  showing  the  points  observed. 

Excretory  System. — If  the  animal  is  a  female,  remove  the 
nidamental  glands,  and  the  kidneys  will  be  seen  in  the  position 
described  for  the  male.  The  kidneys  consist  of: 

1.  The  white,  somewhat  triangular,  glandular  portions  already 
noticed,  extending  from  the  region  of  each  branchial  heart  ante- 
riorly, and  forming  a  portion  of  the  walls  of  the  pre-cavse. 

2.  The  cavities  of  the  organs  lying  ventrally,  and  at  the  sides 
of  the  glandular  portions. 

3.  The  external  openings,  at  the  ends  of  small  papillae,  on 
either  side  of  the  rectum  near  the  anterior  ends  of  the  kidneys. 

Digestive  System. — Remove  the  funnel  and  its  retractor  mus- 
cles and  carefully  lay  the  head  open,  along  the  ventral  side,  to 
expose  the  buccal  mass.  This  is  a  rounded,  muscular  organ, 
with  a  ring  of  tissue  at  its  anterior  end  that  surrounds  the  horny 
jaws.  Examine  the  jaws  and  see  which  is  the  larger.  Trace  the 
narrow  esophagus  from  the  posterior  end  of  the  buccal  mass  back- 
ward. At  the  base  of  the  head  it  enters  the  liver,  a  large,  white 


128  MOLLUSCA. 

organ  that  lies  between  the  retractor  muscles  of  the  head,  and 
extends  from  the  base  of  the  head  to  a  point  dorsal  to  the  exter- 
nal openings  of  the  kidneys.  Lying  close  to  the  esophagus  and 
covered  by  the  anterior  end  of  the  liver  is  an  elongated  median 
livary  gland,  the  duct  from  which  follows  the  esophagus  into 
the  head.  The  esophagus  leaves  the  liver  about  midway  of  its 
length,  and  follows  along  the  ventral  surface  nearly  to  the  stom- 
ach. Before  entering  the  stomach  the  esophagus  passes  the 
pancreas ,  a  white,  lobed  organ  that  lies  just  beneath  the  glandular 
portion  of  the  kidneys,  and  the  systemic  heart,  a  roughly  diamond- 
shaped  organ  that  lies  between  the  branchial  hearts. 

The  stomach  proper  is  a  rather  small,  thick-walled  sac  that 
lies  on  the  right  side  of  the  body,  dorsal  and  posterior  to  the  right 
branchial  heart.  From  the  left  side  of  the  stomach  a  rather 
large  opening  leads  into  a  thin-walled  blind  sac,  the  visceral  sac, 
that  when  filled  with  partly  digested  food,  as  it  frequently  is, 
extends  posteriorly  to  the  end  of  the  body  and  occupies  a  consid- 
erable part  of  the  conical  portion  of  the  body.  When  empty, 
it  is  quite  small  and  inconspicuous. 

The  intestine  leaves  the  stomach  very  near  the  point  the  eso- 
phagus enters,  and  just  anterior  to  the  opening  that  leads  into 
the  visceral  sac.  It  passes  ventrally,  and  becomes  visible  from 
the  surface,  where  its  position  has  already  been  noted. 

Draw  a  figure  showing  the  digestive  system. 

Cut  a  median  sagittal  section  of  the  buccal  mass  and  notice 
the  mouth  cavity,  the  jaws,  the  muscles  that  move  the  jaws,  the 
tongue,  and  the  position  of  the  radula.  Is  the  radula  arranged 
in  the  strap-over-pulley  manner  that  it  is  in  Sycotypus  f 

Draw  a  figure  of  the  section. 

Male  Reproductive  System. — The  position  of  the  penis  has 
already  been  noticed.  Cut  the  tissue  away  from  the  base  of  the 
penis  and  notice  the  swollen  spermatophoric  sac  in  which  the 
spermatophores  are  formed.  Through  the  walls  of  the  base  of 
the  penis  and  the  spermatophoric  sac,  groups  of  slender,  light- 
colored  spermatophores  can  be  seen.  They  will  be  studied  later. 
The  vas  deferens  consists  of  three  distinct  parts: 


LOUGO    PEALII.  129 

(a)  A  narrow,  straight  portion  that  extends  anteriorly  from 
near  the  pointed,  posterior  end  of  the  spermatophoric  sac  and 
lies  along  its  right  side.  This  conducts  the  formed  spermato- 
phores  to  the  spermatophoric  sac,  and  is  sometimes  called  the 
vas  efferens. 

(6)  A  swollen  portion  that  lies  on  the  right  of  the  anterior  end 
of  the  spermatophoric  sac  in  which  the  spermatophores  are 
formed,  the  spermatophoric  tube. 

(c)  A  narrow  and  convoluted  tube  that  leads  posteriorly 
from  the  seminal  vesicle  alongside  the  vas  efferens  and  on  to 
the  capsule  of  the  testis.  This  is  sometimes  referred  to  sepa- 
rately as  the  fas  deferens. 

The  testis  is  a  large,  white  organ  that  extends,  from  the  region 
of  the  stomach,  posteriorly  to  the  end  of  the  body,  dorsal  to  the 
visceral  sac. 

Draw  a  figure  of  the  male  reproductive  system. 

Open  the  base  of  the  penis  and  remove  a  number  of  spermato- 
phores. Place  them  in  a  watch-glass  in  water  and  examine 
with  a  microscope.  Notice: 

1.  The  sheath. 

2.  The  packet  of  spermatozoa. 

3.  The  spiral  discharging  portion. 
Draw. 

Why  are  the  spermatozoa  contained  in  spermatophores? 

Female  Reproductive  System. — The  opening  of  the  oviduct 
has  already  been  noticed.  Observe: 

(a)  The  large,  swollen  portion,  the  oviducal  gland,  that  lies 
dorsal  to  the  left  branchial  heart. 

(6)  The  oviduct  leaving  the  dorsal  portion  of  the  gland.  The 
oviduct  is  long  and  convoluted,  and  is  frequently  filled  wrth  eggs. 
This  depends  on  the  season  of  the  year. 

(c)  The  lighter  colored,  greatly  lobulated  ovary,  also  fre- 
quently filled  with  eggs,  lying  dorsal  to  the  oviduct  and  visceral 
sac  and  extending  from  the  region  of  the  stomach  to  the  end  of 
the  body.  The  ovary  is  inclosed  in  a  capsule  from  which  the 
oviduct  leads. 
9 


*'130  MOLLTJSCA. 

The  nidamental  glands  have  been  studied  and  removed. 

Draw  a  figure  of  the  female  reproductive  system. 

Circulatory  System. — An  injected  specimen  is  desirable.  The 
blood  that  has  been  supplied  to  the  body  in  general  is  collected 
by  veins  and  carried  to  the  branchial  hearts.  The  vessels  that 
collect  the  blood  are: 

1.  The  pre-cavce.    A  single  vessel  carries  the  blood  from  the 
head  to  the  anterior  ends  of  the  kidneys.     Here  the  vessel  divides 
into  right  and  left  pre-cavse  that  are  intimately  connected  with 
the  kidneys.    The  pre-cavse  diverge  near  the  posterior  ends  of 
the  kidneys  and  enter  the  corresponding  branchial  hearts. 

2.  The  post-cavce.    A  pair  of  very  large  vessels  that  return 
blood  from  the  posterior  end  of  the  body.     They  join  the  corre- 
sponding pre-cavae  near  the  anterior  borders  of  the  branchial 
hearts. 

3.  The  mantle-veins.    These  return  blood  to  the  branchial 
hearts  from  the  anterior  portion  of  the  mantle. 

The  blood  that  is  received  by  each  branchial  heart  is  sent 
into  the  corresponding  gill  through  a  vessel  that  leaves  the  heart 
near  the  opening  of  the  mantle  vein,  and  runs  along  the  side  of 
the  gill  that  is  attached  to  the  mantle. 

The  blood  is  collected  from  each  gill  by  a  large  branchial  vein 
that  runs  along  the  ventral  side  of  the  gill,  and  enters  the  sys- 
temic heart. 

Draw  a  figure  showing  the  vessels  connected  with  the  branchial 
hearts. 

Expose  the  systemic  heart  by  carefully  removing  the  superfi- 
cial tissue  between  the  branchial  hearts,  and  notice  that  it  is  not 
symmetrical.  Its  lateral  angles  receive  the  branchial  veins  and 
it  gives  rise  to  an  artery  from  each  of  the  other  two  angles. 

The  posterior  aorta  divides  almost  immediately  into  three 
large  vessels.  These  are: 

(a)  The  median  mantle  artery  which  follows  the  edge  of  the 
ventral  mesentery  to  the  mantle. 

(6)  A  pair  of  lateral  mantle  arteries  which  diverge  posteriorly 
and  supply  the  two  sides  of  the  mantle.  Besides  these  large 


LOLIGO  PEALH.  131 

vessels  there  is  a  small  vessel  that  runs  anteriorly  over  the  ven- 
tral surface  of  the  heart  and  supplies  the  ink  gland  and  rectum, 
and  another  one  that  runs  dorsally  and  posteriorly  to  supply  part 
of  the  reproductive  system. 

(c)  From  the  dorsal  surface  of  the  heart,  near  its  anterior 
end,  a  small  vessel  passes  over  the  anterior  and  dorsal  surfaces 
of  the  stomach  and  finally  passes  into  the  gonad. 

The  anterior  aorta  is  larger  than  the  posterior  aorta.  From 
the  anterior  angle  of  the  heart,  which  is  to  the  right  of  the  median 
line,  it  follows  a  straight  course  alongside  the  esophagus  to  the 
head.  A  number  of  small  vessels  are  given  off  along  its  course, 
and  it  is  finally  distributed  to  the  head  and  arms. 

Draw  the  vessels  connected  with  the  systemic  heart,  into  the 
figure  you  have  just  made. 

Nervous  System. — The  stellate^ganglia  may  be  seen  through 
the  transparent  lining  of  the  mantle,  on  either  side  of  the  neck, 
where  the  body  joins  the  mantle.  They  send  nerves  to  the  man- 
tle and  are  joined  to  ganglia  in  the  head  (the  infra-esophageal) 
by  connectives.  Why  does  the  mantle  need  such  large,  special 
ganglia?  Other  small  ganglia  are  situated  in  the  body,  but  the 
large  and  important  ones  are  grouped  in  the  head,  where  they  are 
supported  and  protected  by  cartilages. 

With  a  razor  make  a  median  sagittal  section  of  the  head  of 
a  squid  and  notice: 

1.  Dorsal  to  the  esophagus  a  rounded  mass,  the  supra-eso- 
phageal  ganglion,  which  is  supposed  to  represent  the  fused  cere- 
bral ganglia. 

2.  Ventral  to  the  esophagus  the  elongated  infra-esophageal 
ganglion,  which  is  supposed  to  represent  the  fused  pedal  and 
visceral  ganglia  and  (together  with  the  masses  that  connect  the 
supra-  and  infra-esophageal  ganglia  around  the  esophagus)  the 
pleural  ganglia. 

3.  The  anterior  prolongation   of  the  infra-esophageal  gan- 
glion to  form  the  pro-pedal  portion,  which  supplies  nerves  to  the 
arms. 

4.  The  small  supra-buccal  ganglia,  lying  dorsal  to  the  esoph- 
agus, and  a  little  further  anterior  than  the  ends  of  the  pro-pedal 


132  MOLLUSCA. 

portion.  These  are  connected  by  connectives  with  the  supra- 
esophageal  ganglia.  .- 

5.  The  infra-buccal  ganglia,  about  the  same  size  as,  and  lying 
ventral  to,  the  supra-buccal  ganglia,  and  connected  with  them 
by  connectives  that  run  around  the  esophagus. 

Draw  a  figure  of  a  sagittal  section  of  the  head. 

Two  large  ganglia,  the  optic  ganglia,  lie  against  the  eyes 
and  will  be  seen  in  cross-sections  of  the  head  that  will  be  studied 
later.  A  dissection  of  one  side  of  the  head  will  show  one. 

Open  the  animal  along  the  mid-dorsal  line  and  find  the  pen 
which  is  embedded  in  the  mantle.  After  exposing  it  for  its 
full  length,  turn  the  flaps  aside  and  see  that  it  lies  in  a  pocket. 
It  probably  represents  a  modified  shell  that  has  become  entirely 
inclosed  by  the  mantle.  What  is  its  function? 

Pull  the  pen  out  of  the  mantle  and  draw  it. 

With  a  razor  make  cross-sections  of  a  squid,  a  quarter  of  an 
inch  thick,  and  arrange  them  in  order,  in  a  little  water,  as  they 
are  made.  Identify  the  parts  you  have  found  in  dissection. 

Make  drawings  of  the  sections  that  pass  through  the  infra-eso- 
phageal  ganglion,  through  the  eyes,  through  the  liver,  and  through 
the  heart. 

If  time  permits,  study  prepared  sections  that  have  pre- 
viously been  made.  The  structure  of  the  eye  and  the  positions 
of  the  parts  of  the  nervous  system  should  receive  special  atten- 
tion. 

Specimens  of  other  cephalopods,  such  as  Octopus  and  Nau- 
tilus, should  be  compared  with  the  squid  and  the  adaptations 
that  fit  them  for  their  particular  lives  noted. 

Brooks:  The  Development  of  the  Squid  (Loligo  Pealii).  Mem.  Bost. 
Soc.  Nat.  Hist.,  1880. 

:  Handbook  of  Invertebrate  Zoology. 

Drew:  Sexual  Activities  of  the  Squid.  I.  Copulation,  Egg-laying  and  Fer- 
tilization. Jour.  Morph.,  22,  1911. 

Griffin :  The  Anatomy  of  Nautilus  pompilius.  Mem.  Nat.  Acad.  Sci.,  8, 1900. 

Vialleton:  Recherches  sur  les  primieres  phases  du  deVeloppment  de  la  Seiche 
(Sepia  officinalis).  Ann.  Sci.  Nat.  (7)  Zool.,  6,  1888. 

Willey:  Contribution  to  the  Natural  History  of  the  Pearly  Nautilus. 
Willey's  Zool.  Results.  4,  Cambridge  Univ.  Press,  1902. 

Williams:  The  Anatomy  of  the  Common  Squid,  Loligo  pealii.  Amer. 
Mus.  Nat.  Hist. 


ARTHROPODA. 

With  segmented  bodies  that  are  provided  with  segmented 
appendages. 

CLASS  1.  Crustacea. 

Usually  aquatic.     With  a  more  or  less  hardened 
outer  covering  and  many  thoracic  appendages. 
Subclass  1.  Entomostraca. 

Usually  small.  Appendages  little  differentiated. 
The  number  of  post-cephalic  segments  variable. 

Order  1.  Phyllopoda. 

Appendages  with  leaf-like  expansions.  (Bran- 
chipus,  Daphnia.) 

Order  2.  Ostracoda. 

Free-swimming,  with  the  body  inclosed  in  a  bi- 
^  valve  shell.     Seven  pairs  of  appendages.     (Cy- 

pris.) 

Order  3.  Copepoda. 

Body  elongated  and  distinctly  segmented  (ex- 
cept in  parasitic  forms).  Four  or  five  pairs  of 
biramous  appendages.  (Cyclops,  Argulus.) 

Order  4.  Cirripedia. 

Comparatively  large  and  usually  attached.     Usu- 
ally  with   six   pairs   of   biramous   appendages. 
Forms  that  are  not  parasitic  are  covered  by  cal- 
careous plates.     (Lepas,  Balanus.) 
Subclass  2.  Malacostraca. 

Usually  of  considerable  size  and  generally  highly 
organized.  Except  in  one  order,  thorax  of  eight 
and  abdomen  of  seven  segments. 

Order  1.  Phyllocarida. 

Body  inclosed  in  a  large,  bivalve  cephalic  cara- 
pace. Abdomen  of  eight  segments.  Thoracic 
segments  free  from  the  head.  (Nebalia.) 

Order  2.  Schizopoda. 

Thoracic  appendages  all  biramous.    Shrimp-like 
in  shape.     (Mysis.) 
133 


134  AETHKOPODA. 

Order  3.  Decapoda. 

Thoracic  segments  united  with  the  head.  Three 
pairs  of  maxillipeds  and  five  pairs  of  legs,  of 
which  the  first  bear  heavy  pincers.  (Homarus, 
Cambarus,  Crangon,  Eupagurus,  Hippa,  Callinec- 
tes,  Cancer.) 

Order  4.  Stomatopoda. 

Five  anterior  thoracic  legs  are  maxillipeds.  Eyes 
stalked.  Gills  borne  on  abdominal  segments. 
(Squilla.) 

Order  5.  Cumacea. 

Two  anterior  thoracic  legs  are  maxillipeds.  Eyes 
sessile.  Small  shrimp-like  forms.  (Diastylis.) 

Order  6.  Arthostraca. 

First  and  sometimes  second  thoracic  segments 
fused  with  the  head.    Eyes  usually  sessile.     (Tal- 
orchestia,  Gammarus,  Caprella,  Porcellio.) 
CLASS  2.  Arachnoidea. 

Head  and  thorax  fused  and  bearing  six  pairs  of 
appendages.     Respiratory  organs  lamellate  and 
abdominal  or  replaced  by  tracheae. 
Subclass  1.  Gigantostraca. 

With  lamellate  abdominal  gills.    Coxal  joints  of 
legs  used  as  jaws.    Marine.     (Limulus.) 
Subclass  2.  Arachnida. 

Respiration  by  lamellate  lungs  or  tracheae.  Four 
pairs  of  walking  legs.  Mostly  terrestrial. 

Order  1.  Scorpionida. 

Abdomen  segmented,  posterior  portion  slender 
and  very  flexible,  ending  in  a  sting.  Four  pairs 
of  lung-books.  Pedipalpi  chelate.  (Buthus.) 

Order  2.  Pseudoscorpionida. 

Abdomen  segmented,  without  slender  posterior 
portion  or  sting.  Pedipalpi  chelate.  Respira- 
tion by  tracheae.  (Chelifer.) 

Order  3.  Pedipalpida. 

Abdomen  flattened  and  segmented.  Pedipalpi 
simple  or  chelate.  Two  pairs  of  lung-books. 
(Phrynus.) 

Order  4.  Solpugida. 

Body  composed  of  three  segments.  Chelicerse 
chelate.  Pedipalpi  elongate,  simple.  Respira- 
tion by  tracheae.  (Galeodes.) 


AETHEOPODA.  135 


Order  5.  Phalangida. 

Body  short  and  oval.  Abdomen  composed  of 
six  segments.  Chelicerse  chelate.  Pedipalpi 
and  legs  very  long  and  slender.  Respiration  by 
tracheae.  (Phalangium.) 

Order  6.  Araneida. 

Abdomen  unsegmented  and  usually  distinct. 
Chelicerae  end  in  claws  that  are  provided  with 
poison  glands.  Lung-books  and  sometimes  tra- 
cheae also  are  present.  Spinnerets  present  on  the 
abdomen.  (Epeira,  Agalena.) 

Order  7.  Acarida. 

Body  not  divided  into  regions.     Biting  or  pierc- 
ing and  sucking  mouth-parts.     Respiration  by 
tracheae    or    through    integument.     (Sarcoptes, 
Dermacentor.) 
Supplementary  to  the  Arachnoidea. 

Pycnogonida. 

(Doubtfully  referred  to  the  group.)  Body  com- 
posed of  segmented  cephalothorax  and  vestigial 
abdomen.  Legs  very  long,  angular,  and  con- 
taining portions  of  the  viscera.  No  special 
respiratory  organs.  (Phoxichilidium.) 
CLASS  3.  Onychophora. 

Elongated  bodies  with  some  annelid-like  charac- 
ters.   Appendages  short,  numerous,  and  creased 
rather  than  jointed.     Respiration  by  means  of 
tracheae.    (Peripatus.) 
CLASS  4.  Myriapoda. 

Generally  elongated  bodies  with  numerous 
jointed  appendages.  A  distinct  head  bearing 
ocelli,  antennae,  and  jaws  is  present.  Respira- 
tion by  means  of  tracheae. 

Order  1.  Symphyla. 

With  not  more  than  twelve  leg-bearing  trunk 
segments.  A  single  pair  of  branching  tracheae. 
(Scolopendrella.) 

Order  2.  Chilopoda. 

With  numerous  trunk  segments,  each  with  a  sin- 
gle pair  of  legs.  First  pair  of  trunk  appendages 
forming  poison  jaws.  Body  dorso-ventrally  com- 
pressed. (Lithobius.) 


136  ARTHKOPODA. 

Order  3.  Diplopoda. 

With  numerous  trunk  segments,  each  with  two 
pairs  of  legs.  No  poison  jaws.  Body  not  com- 
pressed. (Julus.) 

Order  4.  Pauropoda. 

With  ten  trunk  segments  and  nine  pairs  of  legs. 
(Pauropus.) 
CLASS  5.  Insecta. 

Body  divided  into  head,  thorax,  and  abdomen. 
Three  pairs  of  thoracic  legs  and  generally  one  or 
two  pairs  of  wings. 

Order  1.  Thysanura. 

No  metamorphosis.  No  wings.  Mouth-parts 
usually  mandibulate.  Some  forms  show  vestigial 
abdominal  appendages.  (Lepisma,  Sminthurus.) 

Order  2.  Orthoptera. 

Metamorphosis  direct.  Two  pairs  of  wings  usu- 
ally present,  of  which  the  anterior  are  usually 
tough  and  protect  the  more  delicate  posterior 
ones.  Mouth-parts  mandibulate.  (Acridium, 
Gryllus,  Periplaneta.) 

Order  3.  Neuroptera. 

Metamorphosis  direct.  Two  pairs  of  netted 
veined  wings  usually  present.  Mouth-parts  man- 
dibulate. Prothorax  free.  (Libellula,  Termes, 
Hexagenia.) 

Order  4.  Hemiptera. 

Metamorphosis  direct.  Two  pairs  of  wings 
usually  present.  Mouth-parts  piercing  and 
suctorial.  (Benacus,  Cicada,  Pediculus,  Aphis.) 

Order  5.  Diptera. 

Metamorphosis  indirect.  Wings,  when  present, 
one  pair  and  membranous.  Mouth-parts  sucto- 
rial. (Culex,  Tabanus,  Musca.) 

Order  6.  Lepidoptera. 

Metamorphosis  indirect.  Two  pairs  of  scaly 
wings.  Mouth-parts  suctorial.  (Platysamia, 
Anosia,  Philampelus.) 

Order  7.  Coleoptera. 

Metamorphosis  indirect.  Membranous  hind 
wings  folded  and  covered  by  modified  fore 
wings,  the  elytra.  Mouth-parts  mandibulate. 
(Lachnosterna,  Doryphora.) 


HOMARUS  AMEEICANUS.  137 

Order  8.  Hymenoptera. 

Metamorphosis  indirect.  Two  pairs  of  membra- 
nous wings.  Mouth-parts  suctorial  and  man- 
dibulate.  (Apis,  Vespa.) 

Exner:  Die  Physiologie  der  facettirten  Augen  von  Krebsen  und  Insecten, 

1891. 
Prentiss:  The  Otocyst  of  Decapod  Crustacea:  Its  Structure,  Development, 

and  Functions.     Bui.  Mus.  Comp.  Zool.  Harvard,  36,  1901. 
Watase":  On  thetMorphology  of  the  Compound  Eyes  of  Arthropods. 

Stud.  Biol.  Lab.  Johns  Hopkins  Univ.,  4. 


CRUSTACEA. 

HOMARUS  AMERICANUS.    (Lobrte*.*) 

These  animals  are  not  generally  found  where  they  can  be 
readily  observed  in  nature,  but  many  valuable  observations  can 
be  made  on  specimens  confined  in  aquaria.  If  other  animals 
are  present  in  the  aquarium  notice  the  position  of  defense  that 
is  taken.  In  nature  the  animal  probably  spends  much  of  its 
time  under  rocks  with  the  anterior  end  of  the  body  turned  to- 
ward the  opening.  In  this  position  both  sense  organs  and 
weapons  are  in  the  proper  position  for  attack  or  defense.  Notice 
how  the  appendages  are  used.  Are  the  sense  organs  moved  fre- 
quently? Why  are  the  eyes  on  stalks?  What  appendages  are 
used  in  walking?  Are  all  of  these  appendages  used  in  just  the 
same  way?  Does  the  animal  move  equally  well  in  all  directions? 
Perhaps  you  can  make  the  animal  swim;  if  so,  observe  the 
method.  Feed  a  specimen  with  portions  of  a  clam  or  fish,  and 
see  how  food  is  torn  to  pieces  and  transferred  to  the  mouth,  and 
determine,  if  possible,  how  the  mouth  appendages  are  used. 

External  Anatomy. — As  in  Nereis,  the  body  is  segmented. 
The  metameres  of  the  head  and  thorax,  however,  are  immova- 
bly fused  to  form  a  cephalo-thorax.  This  is  covered  dorsally  by 
-a  single  piece,  the  carapace. 

1.  Note,  on  the  carapace,  the  cervical  groove  between  the  head 

1  These  directions  may  be  used  for  the  crayfish  without  much  modifi- 
cation. The  smaller  size  of  these  animals  will  make  it  more  difficult  to 
trace  some  of  the  nerves  and  blood-vessels 


138  ABTHROPODA. 

and  thorax,  and  the  beak  or  rostrum  forming  an  anterior  spine. 
The  ventro-lateral  edge  of  the  carapace  is  not  attached.  A  flat 
object  thrust  between  it  and  the  body  passes  into  the  gill  cham- 
ber. This  free  plate  of  the  carapace  is  called  the  gill-cover. 
Do  you  know  why  the  edge  of  the  carapace  is  free?  Notice  the 
hair-like  spines  along  its  free  border.  What  purpose  do  these 
serve  ? 

2.  The  abdomen  is  composed  of  seven  movable  segments, 
each  bearing  a  pair  of  jointed  appendages  except  the  last,  which 
is  sometimes  not  considered  a  true  segment  and  is  called  the 
telson.    Each  abdominal  segment  consists  of  a  dorsal  piece,  the 
tergum,  which  is  continued  as  a  free  plate  laterally  (the  pleurori), 
and  of  a  ventral  piece,  the  sternum.    Move  the  abdominal  seg- 
ments and  see  where  they  are  hinged.     How  are  the  terga  and 
sterna  arranged  to  allow  free  movement?    In  the  thorax  the 
sterna,  though  fused,  can  be  distinguished.    There  are  eight 
segments  in  the  thorax. 

3.  Appendages. — Aside  from  the  stalked  eyes,  whose  homol- 
ogy  with  true  appendages  is  doubtful,  there  are  nineteen  pairs. 
These  are,  counting  from  before  backward:  antennules,  antenna, 
six  pairs  of  mouth  appendages,  five  pairs  of  walking  legs  (pereio- 
pods),  of  which  the  first  are  the  claws  or  chelce,  and  six  pairs  of 
swimmerets   (pleopods).     In  the  male,  the  first  two   pairs   of 
pleopods  are  modified  to  form  copulatory  organs. 

(a)  Turn  one  of  the  fifth  pair  of  pleopods  forward  and  exam- 
ine its  posterior  aspect.     It  consists  of  a  basal  piece,  the  proto- 
pod,   a  lateral  branch,  the  exopod,  and  a  median  branch,  the 
endopod.    This  branched   type  of  appendage  is  designated  as 
biramous.     What  is  its  use?     Compare  with  this  the  modified 
sixth  pair  of  pleopods,  called  the  uropods. 

Make  a  drawing  of  one  of  the  -fifth  pleopods. 

(b)  In  front  of  the  chelae  will  be  seen  the  sixth  pair  of  mouth 
appendages,  the  third  maxillipeds.     Remove  that  of  the  right 
side  and  compare  it  with  the  fifth  pleopod.     In  addition  to  the 
protopod,  exopod,  and  endopod,  it  bears  a  long  blade,  the  epipod, 
which  extended  into  the  gill  chamber.     The  protopod  is  com- 


HOMARUS   AMERICANTTS.  139 

posed  of  two  segments,  coxopod  and  basipod;  the  endopod  of  five, 
segments,  ischipod,  meropod,  carpopod,  propod,  and  dactylopod. 
The  exopod  is  composed  of  one  long  and  many  short  segments. 
How  is  the  appendage  modified  to  serve  in  feeding? 
Make  a  drawing  of  the  third  maxilliped. 

(c)  Remove  the  remaining  five  mouth  appendages  and  com- 
pare each  with  the  third  maxilliped.     These  are,  beginning  pos- 
teriorly, the  second  maxilliped,  first  maxilliped,  second  maxilla 
(with   a  broad   paddle,  the  scaphognathite,  the  use  of  which 
should  be  understood),   first   maxilla,  and  the  mandible.    Just 
back  of  the  mandibles   are  two  small  flaps,  the  paragnatha, 
which  are  not  true  appendages.    Do  you  understand  the  use 
of  each  of  these  appendages?    Most  of  the  appendages  have 
parts  that  may  be  compared  with  the  typical  biramous  appen- 
dage, but  they  are  much  modified  to  serve  special  functions,  and 
the  exact  homologies  are  not  important.     Between  the  man- 
dibles note  the  mouth,  bounded  in  front  by  the  labrum. 

Drawings  of  these  appendages  may  be  made  if  time  permits. 

(d)  The  antennce  are  biramous.     Notice  on  the  ventral  side  of 
the  basal  joint  of  an  antenna  the  opening  of  the  green  gland  or 
nephridium. 

(e)  The  antennules,  though  branched,  are  not  considered  to 
be  of  the  biramous  type.     Do  you  know  why?    Remove  one  and 
note  on  the  dorsal  surface  of  the  basal  joint  a  groove  at  whose 
median  extremity  is  a  small  hole,  the  opening  into  the  otocyst. 
Do  you  know  the  probable  function  of  the  antennules  and  of 
the  otocysts?     What  reason  is  there  for  having  both  antennules 
and  antennae? 

(/)  Compare  the  pereiopods  with  the  third  maxilliped. 
Which  is  lacking,  endopod  or  exopod?  Examine  each  of  the 
joints  of  one  of  these  appendages  and  see  in  what  directions 
the  appendage  may  be  moved.  Are  there  any  ball-and-socket 
joints?  Compare  the  chelae  with  the  other  pereiopods  and  see 
how  they  differ.  To  what  part  of  a  chela  does  the  last  segment 
of  the  last  pereiopod  correspond?  What  reason  is  there  for 
having  these  appendages  different?  Do  you  think  the  arrange- 


140  ARTHROPOD A. 

ment  of  the  appendages  would  aid  the  lobster  in  climbing  over 
rough  bottom? 

Open  one  of  the  large  chelae  and  determine  how  the  muscles 
are  arranged  to  control  its  opening  and  closing.  Which  mus- 
cles are  strongest?  Find  how  the  muscles  are  attached  to  the 
"thumb." 

Find  the  openings  of  the  sexual  ducts  on  the  basal  joints  of 
the  pereiopods;  the  last  pair  in  the  male,  the  second  from  the  last 
pair  in  the  female.  In  the  female  there  is  an  opening  into  a 
seminal  receptacle  through  a  triangular  elevation  on  the  ventral 
side  of  the  thorax. 

4.  Gills. — Remove  the  gill-cover  of  the  left  side,  being  care- 
ful not  to  injure  the  gills.  Extending  up  into  the  gill  cavity 
are  seven  epipods  belonging  to  the  three  maxillipeds  and  the 
four  anterior  pereiopods.  They  separate  the  gills  into  groups. 
Each  group  will  be  seen  to  correspond  to  a  segment.  The  gills 
show  three  sorts  of  attachments:  (a)  to  the  appendages  them- 
selves (podobranchs) ,  (b)  to  the  articular  membranes  between 
appendages  and  body-wall  (arthrobranchs) ,  and  (c)  to  the  body- 
wall  itself  (pleurobranchs).  There  are  two  arthrobranchs  in 
some  segments,  one  behind  and  above  the  other.  How  is  the 
current  of  water  forced  through  the  gill-chamber?  What  is 
the  function  of  the  epipods?  What  direction  must  the  water 
take  through  the  gill  chamber  ?  Examine  the  structure  of  a  gill. 
Move  one  of  the  appendages  to  which  a  gill  is  attached  and  see 
the  effect  on  the  gill. 

Internal  Anatomy. — Remove  the  carapace  (beginning  at  the 
middle  of  the  posterior  margin  and  cutting  forward,  holding  the 
cartilage  knife  parallel  with  the  surface)  as  far  laterally  as  the 
upper  limits  of  the  gill  chambers  and  anteriorly  to  the  base  of 
the  rostrum.  What  is  the  pigmented  membrane  for?  Dissect 
it  off  so  underlying  organs  may  be  seen. 

1.  The  chitinous  stomach  lies  near  the  anterior  end  with  the 
ophthalmic  artery  running  along  its  mid-dorsal  line.  Beside  and 
behind  the  stomach  are  two  masses  of  muscle  which  you  have 
severed  from  the  carapace.  These  are  the  mandibular  muscles, 


HOMABUS   AMEBICANUS.  141 

and  each  is  divided  into  an  anterior  and  a  posterior  bundle. 
Lateral  to  these  muscle  masses  are  the  yellow-green  digestive 
glands,  commonly  called  liver.  Between  and  in  front  of  the 
posterior  mandibular  bundle  note  the  gonads,  and  follow  one 
forward  by  pressing  aside  the  muscle  mass.  In  the  male  the 
testis  is  a  slender,  white,  convoluted  cord,  which  ends  blindly 
against  the  side  of  the  stomach.  The  extent  and  position  of  the 
far  thicker  yellow  ovary  is  much  the  same  (unless  the  animal 
be  mature,  in  which  case  it  will  be  found  greatly  enlarged  and 
orange). 

2.  The  heart  extends  through  the  posterior  third  of  the  tho- 
rax.    Remove  the  upper  part  of  the  delicate  pericardium  sur- 
rounding it,  cut  its  arterial  and  other  connections,  and  place  it 
in  water.     Note  the  shape,  the  origin  of  the  arteries,  and  the 
three  pairs  of  ostia.    Do  you  understand  how  it  receives  blood? 

3.  Trace  the  gonads  as  far  as  the  abdomen,  noting  the  single 
anastomosis  between  those  of  opposite  sides  just  in  front  of  the 
heart.     Beneath  the  heart  the  sexual  ducts  are  given  off — vasa 
deferentia  in  the  male,  oviducts  in  the  female.     Trace  one  out- 
ward and  downward  to  its  opening  by  removing  a  portion  of  the 
body-wall  and  of  the  basal  joint  of  the  proper  leg. 

4.  Remove  the  posterior  lateral  body-wall  forward  to  a  posi- 
tion opposite  the  anterior  third  of  the  stomach.     Pull  the  an- 
terior lobe  of  the  liver,  which  extends  beneath  the  stomach, 
outward  and  backward.    The  liver  will  be  seen  to  be  attached 
to  the  pyloric  end  of  the  stomach  (i.  e.,  the  smaller  part,  where 
the  stomach  passes  into  the  intestine).     Cut  this  attachment 
and  note  that  it  is  really  where  the  liver  opens  into  the  stomach. 
Just  back  of  this  point  the  right  and  left  lobes  of  the  liver 
are  connected  by  a  cross-branch  passing  beneath  the  intestine. 
Remove  one  liver  lobe  back  to  the  abdomen.    After  having  the 
circum-esophageal  connectives  pointed  out,  remove  the  stomach  by 
cutting  the  esophagus,  the  intestine,  and  the  bands  of  muscles 
attached  to  the  stomach.     Examine  it  in  water,  noting  the  cardiac 
and  pyloric  parts,  the  chitinous  grinding  and  straining  apparatus 
in  the  interior,  and  the  muscles  and  plates  that  cause  the  move- 


142  ABTHROPODA. 

ments  of  the  grinding  apparatus.    Why  does  a  lobster  with 
chelse  and  six  pairs  of  mouth  appendages  need  a  gastric  mill? 

5.  Between  the  circum-esophageal  connectives  medially  and 
the  large  antennary  muscles  laterally,  note  the  oval  excretory 
organs,  called  the  green  glands.    They  are  covered  by  a  very 
delicate  membrane.     Poke  a  small  hole  in  one  of  the  membranes 
and  with  a  blowpipe  show  that  it  is  really  a  thin  bladder.     Its 
opening  on  the  antenna  has  already  been  seen. 

6.  Remove  the  dorsal  wall  of  the  abdomen  and  trace  the 
posterior  portions  of  the  gonads,  liver  lobes,  and  intestine.     In 
the  sixth  abdominal  segment  the  intestine  swells  to  form  the 
chitin-lined  rectum  and  gives  off  the  blind  intestinal  ccecum. 

Circulatory  and  Nervous  Systems.1  —  Remove  the  carapace  of 
an  injected  specimen  as  before,  also  the  gill-cover  and  gills  on 
one  side. 

1.  There  can  generally  be  seen,  through  the  transparent 
body-wall,  efferent  branchial  veins,  which  return  the  blood  from 
the  gills.    These  unite  into  six  large  ones  which  open  into  the 
pericardium  at  the  side.     Find  these  openings  if  possible.    Do 
you  understand  how  blood  gets  into  the  heart? 

2.  Note,  at  the  anterior  end  of  the  heart,  the  ophthalmic 
artery  and  the  two  antennary  arteries.     Trace  the  former  forward 
to  the  rostrum,  cut  it  on  the  stomach  and  turn  it  forward  for 
future  study.    Trace  the  antennary  arteries  to  the  mandibular 
muscles  and  cut  them  near  the  heart.     Press  the  front  end  of 
the  heart  back  and  note  the  two  small  hepatic  arteries.    Each 
branches  immediately,  one  division  passing  between  the  gonads, 
and  the  other  laterally. 

3.  Remove  the  muscles  on  one  side  of  the  heart  and  examine 
it  from  the  side,  noting  the  great  sternal  artery  extending  down- 
ward, and  the  smaller  dorsal  abdominal  artery  running  back  above 
the  intestine.    Follow  the  latter  through  the  abdomen. 


circulatory  system  of  a  fresh  specimen  may  be  satisfactorily 
injected  with  starch-mass  by  inserting  the  needle  of  a  hypodermic  syringe 
into  the  pericardium  from  the  posterior  margin  of  the  carapace.  The 
operation  is  easily  performed  when  the  distance  to  the  pericardium  is 
understood. 


HOMARUS   AMERICANUS.  143 

4.  Cut  all  arteries  and  remove  the  heart.    Trace  the  anten- 
naries  through  the  mandibular  muscles,  noting  the  branch  to 
the  stomach. 

5.  Remove  the  thoracic  viscera  as  before,  follow  the  circum- 
esophageal  connectives  forward  and  identify  the  cerebral  ganglia 
in  order  not  to  destroy  them. 

6.  Follow  one  antennary  artery  to  the  green  gland,  antennary 
muscle,  eye  muscle,  etc. 

7.  Follow  the  distribution  of  the  ophthalmic  artery. 

8.  Remove  the  intestine  and  muscles  of  the  abdomen,  and  find 
and  trace  forward  the  ventral  nerve  chain.    Notice  the  position 
of  the  ganglia  and  the  nerves  that  leave  them  and  the  connec- 
tives.    In  the  thorax  the  ventral  nerve  chain  passes  beneath  a 
system  of  chitinous  plates  (the  endo-phragmal  skeleton)  and  lies 
in  a  cavity,  the  ventral  blood  sinus.    Note  the  enlarged  sub- 
esophageal  ganglion,  the  cross  commissure  just  back  of  the  esoph- 
agus, the  nerves  to  the  mouth  appendages,  nerves  from  the 
cerebral  ganglia,  and  nerves  from  the  other  ganglia.     What  indi- 
cation is  there  that  the  sub-esophageal  ganglia  represent  more 
than  a  single  pair? 

Sketch  the  nervous  system. 

9.  The  sternal  artery  passes  through  the  ventral  nerve  chain 
and  then  extends  backward  and  forward  as  the  ventral  longitu- 
dinal artery.    Remove  the  nervous  system  and  follow  this  ar- 
tery. 

Draw  a  diagrammatic  cross-section  through  the  thorax,  putting 
in  one  drawing  the  circulation  from  the  heart  through  the  sternal 
artery  to  the  limbs  and  back  through  the  gills  to  the  heart. 

Andrews:  The  Keeping  and  Rearing  of  Crayfish  for  Class  Use.     Nat. 

Stud.  Rev.,  2,  1906. 
:  The  Young  of  the  Crayfishes  Astacus  and  Cambarus.     Smithsonian 

Cont.  to  Knowl.,  35,  1907. 

:  Conjugation  in  the  American  Crayfish.     Am.  Nat.  29,  1895. 

Bumpus:  Movements  of  Certain  Lobsters  Liberated  at  Woods  Hole.     Bui. 

U.  S.  Com.  Fish,  1899. 

:  Embryology  of  the  American  Lobster.     Jour.  Morph.,  5,  1891. 

Herrick:  Natural  History  of  the  American  Lobster.     Bui.  U.  S.  Bur.  Fish, 

29,  1909. 


144  ARTHROPODA. 

Huxley:  The  Crayfish.    An  Introduction  to  the  Study  of  Zoology.     1884. 

Mead:  Habits  and  Growth  of  Young  Lobsters.     Rhode  Island  Com.  In- 
land Fisheries,  21,  1901. 

Pearl  and  Clawson:  Variation  and  Correlation  in  the  Crayfish.     Carnegie 
Inst.  Pub.,  64,  1907. 

Pearse:  Observations  on  Copulation  Among  Crawfishes  with  Special  Refer- 
ence to  Sex  Recognition.     Am.  Nat.,  43,  1909. 

Steele:  Regeneration  of  Crayfish  Appendages.     Univ.  Missouri  Studies,  2, 
1904. 

— :  Regeneration  in  Compound  Eyes  of  Crustacea.     Jour.  Exp.  Zool.,  5, 
1907. 

Williams:  The  Stomach  of  the  Lobster  and  the  Food  of  Larval  Lobsters. 
An.  Rep.  Com.  Inland  Fish.,  Rhode  Island,  37,  1907. 


CALLINECTES  HASTATUS,    (Blue  Crab.) 

Crabs  may  be  found  in  shallow  water  along  shore,  where  they 
may  be  easily  observed  on  quiet  days.  In  what  direction  does 
the  animal  normally  move?  How  are  the  legs  used?  What  is 
the  attitude  of  defense?  Determine  how  the  blue  crab  swims. 
What  do  crabs  apparently  use  for  food  ?  Do  they  conceal  them- 
selves, are  they  protectively  colored,  or  do  they  depend  entirely 
upon  their  weapons  for  defense  ? 

In  studying  the  anatomy  of  the  crab,  constant  comparisons 
should  be  made  with  the  lobster. 

External  Anatomy. — 1.  The  body  is  composed  of  cephalo- 
thorax  and  abdomen.  Dorsally  note  the  shape  of  the  carapace 
and  the  position  of  the  abdomen.  The  size  of  the  abdomen 
differs  in  male  and  female.  Why  should  it  be  larger  in  the 
female? 

2.  Note  the  antennce,  antennules,  and  eyes,   and  see  how  they 
are  packed  away  in  recesses  in  the  carapace.     In  the  living 
animal  see  if  any  of  these  are  frequently  moved. 

3.  The  third  maxillipeds  are  flattened  and  cover  the  other 
mouth  appendages. 

4.  Straighten  the  abdomen  and  note  the  anus.    Compare  the 
abdomen  of  a  male  with  that  of  a  female  and  both  with  that  of  the 
lobster.    The  dorsal  side  of  each  segment  is  covered  by  a  tergum. 
The  covering  between  each  pair  of  pleopods  is  the  sternum,  the 
immovable  flap  lateral  to  them  is  the  pleuron.    Compare  the  ab- 
dominal appendages  or  pleopods  of  a  male  and  a  female. 


CALLINECTES   HASTATUS.  145 

5.  The  ventral  side  of  the  cephalo-thorax  is  covered  by  the 
sternal  plastron.    Note  the  eight  sterna  and  six  pairs  of  lateral 
episterna,  the  anterior  pair  of  which  is  very  small. 

6.  In  the  female  find  the  openings  of  the  oviducts  in  the 
sixth  sternum. 

Make  a  drawing  of  the  ventral  side. 

7.  Expose  the  gill  chamber  and  compare  the  gill  distribution 
with  that  of  the  lobster. 

8.  Remove  the  left  third  maxilliped  entire,  and  compare  it 
with  the  same  appendage  of  a  lobster.    The  protopod  is  com- 
posed of  two  segments  (coxopod  and  basipod).    The  endopod 
has  five  pieces  (ischipod,  meropod,  carpopod,  propod,  and  dactyl- 
opod).     The  exopod  has  two  large  and  many  small  segments. 
Attached  to  the  coxopod  laterally  is  an  epipod  which  extended 
into  the  gill  chamber. 

9.  Remove  the  remaining  mouth  appendages  on  the  left  side 
and  compare  them  with  the  third  maxilliped.     They  are:  second 
maxilliped  bearing  epipod  and  two  small  gills;    first  maxilliped 
with  an  epipod;   second  maxilla  with  a  flattened  exopod,  called 
the  scaphoghathite,  which  is  made  up  of  both  exopod  and  epipod 
and  which  has  a  special  function  that  should  be  understood; 
first  maxilla,  thin  and  leaf-like;  mandible  with  two  hard  rods 
for  the  attachment  of  muscles. 

10.  Detach  and  examine  one  each  of  the  eyes,  antennuks,  and 
antennce.     On  the  flattest  side  of  the  basal  joint  of  the  anten- 
nule  note  a  dark  suture — the  scar  of  the  former  opening  into  the 
otocyst.     Do  you  understand  what  function  is  performed  by  the 
otocysts?    Near  the  base  of  the  antenna  find  the  opening  of  the 
renal  organ  (green  gland). 

11.  Compare  each  of  the  five  walking  legs  (pereiopods)  with 
the  third  maxilliped.     Which  part,  endopod  or  exopod,  is  lack- 
ing?   Which  bear  forceps  or  chelae?    Why  is  this  so?    Note  in 
the  male  the  openings  of  the  sperm  ducts  on  the  coxopods  of  the 
fifth  pair. 

Internal  Anatomy. — Remove  the  entire  dorsal  part  of  the 
carapace. 
10 


146  ARTHROPOD  A. 

1.  Postero-laterally  are  two  firm  prominences,  the  flanks, 
containing  muscles.     What  are  these  muscles  for?    Anterior  to 
these  are  the  gill  chambers  covered  by  a  thin  cuticle.    Remove 
this  and  note  the  gills  with  their  tips  converging  medially. 

2.  Between  the  gill  chambers  and  flanks  is  the  delicate  peri- 
cardium.   Remove  this  and  find  the  heart  with  its  ostia.    An- 
teriorly it  sends  out  an  ophthalmic  artery  and  two  antennary 
arteries.     Just  anterior  to  the  heart  are  muscles  which  were 
attached  to  the  shell.     What  organs  do  they  supply?    The  an- 
tennary arteries  pass  through  the  heads  of  a  pair  of  the  muscles. 

3.  In  front  of  the  gill  chambers  are  the  gonads.     In  the  female 
the  orange  ovary  will  be  seen  lying  on  the  yellow  liver.     In  the 
male  the  slender,  wavy,  white  cord,  the  testis,  lies  in  approxi- 
mately the  same  position. 

4.  The  heart  is  attached  to  the  pericardium  by  muscular 
strands.     Cut  these,  and  the  three  anterior  arteries,  and  remove 
the  heart,  noting  the  two  hepatic  arteries  beneath  the  antennary 
arteries,  the  great  sternal  artery  passing  downward  from  the 
under  side,  and  the  small  abdominal  artery  just  behind  the  last. 

Draw  dorsal  and  ventral  views  of  the  heart  to  show  the  ostia 
and  the  origins  of  arteries. 

5.  Cut  across  a  gill  and  notice  its  afferent  and  efferent  vessels. 
The  latter  is  continuous  with  one  of  the  sinuses  which  empty 
into  the   pericardial  cavity.     Can  you  determine  how  many 
sinuses  there  are?    Do  you  understand  how  the  heart  receives 
blood? 

Reproductive  System. — Beginning  antero-laterally,  on  one 
side,  dissect  out  the  reproductive  organs,  noting  at  the  same  time 
the  distribution  of  arteries. 

(a)  Female  reproductive  organs. — Each  ovary  passes  inward 
and  backward,  anastomoses  with  the  one  of  the  other  side  be- 
hind the  stomach,  and  extends  back  to  the  abdomen.  On  a 
level  with  the  posterior  part  of  the  stomach  a  branch  passes  down- 
ward and  outward  and  is  continuous  with  a  dense,  white  organ, 
the  seminal  receptacle.  Leave  this  receptacle  in  place  but  remove 
the  entire  ovary. 


CALLINECTES   HASTATUS.  147 

(b)  Male  reproductive  organs. — The  usually  slender  testis 
which  is  large  during  the  season  of  activity  passes  inward  and 
backward,  anastomoses  with  its  fellow  of  the  other  side  behind 
the  stomach,  and  is  continued  as  a  thick,  much-coiled  tube,  the 
vas  deferens,  to  the  median  side  of  the  flank.  It  then  runs  for- 
ward nearly  to  the  stomach,  turns  back  again,  and  enters  the 
substance  of  the  flank.  By  removing  the  top  of  the  flank  and 
the  upper  side  of  the  coxopod  of  the  swimming  leg,  it  can  be  fol- 
lowed to  its  external  opening. 

Digestive  System. — (a)  The  liver  fills  all  of  the  body-cavity  not 
occupied  by  other  organs.  Remove  the  portion  of  it  that  is  in  the 
region  of,  and  anterior  to,  the  stomach,  noting  its  connection 
with  the  alimentary  tract. 

(6)  The  stomach  is  a  chitinous  box  divided  into  a  larger  car- 
diac and  a  smaller  pyloric  portion.  On  each  side  find  the  duct 
from  the  liver,  and  a  slender,  white,  coiled  tube,  the  pyloric 
caecum. 

(c)  Follow  the  delicate  intestine  back  beneath  the  heart. 
Between  the  posterior  edges  of  the  flank  is  a  white  mass  composed 
of  a  coiled  tube,  the  intestinal  ccecum.    Remove  the  terga  of  the 
abdominal  segments,  follow  this  caecum  to  its  connection  with 
the  intestine,  and  follow  the  latter  to  the  anus,  noting  its  chiti- 
nous lining. 

(d)  Cut  out  the  alimentary  tract,  open  the  stomach,  and 
examine  the  grinding  and  straining  apparatus. 

Make  a  drawing  of  the  alimentary  canal. 

Excretory  Organs. — Examine  the  antennary  gland  (green 
gland)  on  the  inside  of  the  carapace  opposite  the  base  of  the 
antenna.  It  consists  of  a  thin  bladder,  and,  anterior  to  this,  a 
mass  composed  of  a  coiled  tube  which  opens  at  the  base  of  the 
antenna. 

Nervous  System. — Find  the  ring  of  ganglia  around  the 
ventral  end  of  the  sternal  artery.1  Trace  the  nerves  from  this 
to  the  appendages  and  to  the  small  abdomen.  Trace  the  circum- 

*In  a  fresh  specimen  the  ganglia  can  be  more  easily  studied  after 
treating  them  with  strong  alcohol  for  a  moment. 


148  ARTHROPODA. 

esophageal  connectives  around  the  gullet  (they  anastomose  just 
behind  it)  to  the  cerebral  ganglia.  Along  with  the  distribution 
of  the  ophthalmic  and  antennary  arteries,  trace  the  nerves  from 
the  cerebral  ganglia  to  the  eyes,  antennse,  antennules,  etc.  Why 
should  the  nervous  system  be  more  concentrated  than  it  is  in  the 
lobster?  . 

Make  a  drawing  of  the  nervous  system. 

Brooks:  Hand-book  of  Invertebrate  Zoology. 

Gurney:  Metamorphosis  of  Corystes.    Quart.  Jour.  Micro.  Sci.,  46,  1902:' 

EUPAGURUS.    (Hermit  Crab.) 

Examine  a  living  specimen  and  see  how  it  moves,  and  how 
the  aperture  of  the  shell  is  closed  by  the  two  large  claws  when 
the  animal  withdraws. 

With  a  hammer  crack  the  shell  away  from  the  animal  and 
examine  the  twisted  abdomen. 

1.  Has  it  lost  its  symmetry  in  appendages  as  well  as  in  shape? 

2.  How  many  of  the  appendages  have  been  retained  ?    What 
is  the  function  of  these  appendages? 

3.  Remove  several  other  specimens  from  their  shells  and 
place  them  in  a  dish  of  sea-water  together?    Do  they  seem  to 
understand  that  they  are  not  protected? 

4.  Place  an  empty  shell  in  the  dish  and  see  what  happens. 

5.  Put  more  empty  shells  in  the  dish,  but  be  sure  they  are 
not  quite  large  enough  for  the  crabs.    Then  add  some  larger 
shells  and  watch  the  crabs  test  them  to  see  which  will  serve 
best. 

A  drawing  is  desirable. 

Thompson:  The  Metamorphoses  of  the  Hermit  Crab.    Proc.  Bost.  Soc.  Nat. 
Hist.,  31,  1903. 

HIPPA.    (Sand  Mole.) 

On  sand  beaches,  between  low-  and  high-water  mark,  there 
may  frequently  be  seen  the  shallow  depressions  that  mark  the 
places  where  these  animals  have  burrowed.  They  may  be  dug 
out  with  a  shovel,  but  they  quickly  disappear  again. 


SQUILLA.  149 

1.  Notice  their  shape  and  the  ease  and  rapidity  with  which 
they  burrow. 

2.  Place  specimens  in  a  dish  containing  sand  and  a  little  sea- 
water  and  try  to  determine  just  how  the  burrowing  is  done.    This 
may  frequently  be  done  by  holding  a  specimen  so  it  just  touches 
the  sand.     Which  end  goes  into  the  sand  first?    Notice  the  posi- 
tions in  which  the  appendages  are  held.     Does  this  have  any- 
thing to  do  with  the  direction  in  which  it  burrows?    Does  the 
animal  jump  or  crawl?    In  what  direction  and  how  can  it  swim? 

3.  Examine  the  body  and  see  if  it  is  divided  into  head,  thorax, 
and  abdomen.    Why  has  the  telson  such  a  peculiar  shape  ? 

4.  Examine  the  appendages, 
(a)  The  stalked  eyes. 

(6)  The  biramous  antennules  and  the  exceedingly  long,  feath- 
ery antennas.  What  is  the  usual  position  of  the  antennae  ? 

(c)  The   mouth   appendages.    Are   strong,   hard   mandibles 
present  ?    What  must  the  character  of  the  food  be  ? 

(d)  The  thoracic  appendages.     How  many  are  there?    Are 
they  similar?    Are  there  any  chelae? 

(e)  The  abdominal  appendages.    Are  they  all  alike?    What 
functions  are  performed  by  them? 

Make  a  drawing. 

SQUILLA. 

Compare  the  animal  carefully  with  the  lobster,  noting  all  of 
the  important  differences.  The  posterior  three  thoracic  seg- 
ments are  free.  The  male  possesses  a  copulatory  organ  on  the 
basal  joint  of  the  last  thoracic  leg.  In  the  female  the  opening  of 
the  oviducts  is  in  the  mid-ventral  line,  on  the  antepenultimate 
thoracic  segment.  Examine  the  chelae  and  compare  them  with 
the  chelae  of  a  lobster.  Are  they  homologous  appendages  in  the 
two  animals?  If  you  have  living  specimens,  study  their  move- 
ments while  walking  and  swimming. 

A  drawing  of  a  side  or  ventral  view  will  be  profitable. 

Internal  Anatomy. — 1.  Remove  the  top  of  the  carapace  and 
abdomen.  Beneath  the  muscles  note  the  elongated,  white  tube, 


150  ARTHROPOD  A. 

the  heart,  which  extends  from  the  stomach  to  the  fifth  abdomi- 
nal segment.  The  anterior  end  is  slightly  enlarged  and  gives 
rise  to  the  anterior  aorta.  The  posterior  end  gives  rise  to  a 
posterior  aorta.  Note  lateral  arteries  and  ostia.  Remove  the 
heart. 

2.  Beneath  the  heart,  in  the  male,  is  a  whitish,  pigmented, 
flattened  mass  which  consists  of  two  convoluted  tubes,  the  testes. 
Cut  this  mass  across  between  the  second  and  third  abdominal 
segments  and  force  it  posteriorly.    The  two  testes  are  continu- 
ous posteriorly.     Follow  them  anteriorly  and  find  the  slender, 
dense,   coiled  vasa  deferentia  passing  outward  and  downward 
at  the  posterior  end  of  the  third  thoracic  segment.    Cut  them  and 
lay  them  back  where  they  can  be  dissected  later.    The  testes  ex- 
tend forward  to  the  region  of  the  stomach.     Remove  the  testes. 

3.  Beneath  the  heart,  in  the  female,  are  the  two  ovaries. 
Trace  them  forward  and  backward,  and  find  the  very  slender 
oviduct  that  extends  from  each  outward  and  downward  in  the 
region  of  the  antepenultimate  thoracic  segment.     Remove  the 
ovaries,  deferring  the  tracing  of  the  oviduct. 

4.  Beneath  the  reproductive  organs,  in  both  sexes,  is  the 
granular  liver.     This  consists  of  two  lobes  which  extend  from  the 
stomach  to  the  end  of  the  telson.     They  form  saccular  diverticula 
between  segments  and  in  the  telson.     Where  do  they  open  into 
the  alimentary  tract? 

5.  Free  the  intestine,  which  is  between  the  lobes  of  the  liver. 
The  rectum  is  in  the  sixth  abdominal  segment. 

6.  Pull  back  the  anterior  end  of  the  stomach,  identify  the 
circum-esophageal  connectives,  in  order  not  to  destroy  them, 
and  free  the  stomach  by  cutting  the  esophagus  and  intestine. 
Examine  the  stomach  under  water. 

7.  Trace  the  nerve  chain.    What  ventral  ganglia  are  fused? 
The  cerebral  ganglia  are  most  easily  exposed  by  slicing  away, 
very  superficially,  the  dorsal  surface  of  the  rostrum  and  pressing 
the  eye  muscles  apart. 

A  drawing  of  the  nervous  system  will  be  profitable. 

8.  Trace  the  genital  ducts  to  their  external  openings. 


MYSIS.      TALORCHESTIA.  151 


MYSIS. 

If  living  specimens  are  to  be  had,  watch  them  swim,  and  de- 
termine what  parts  are  used  in  swimming.  Does  the  animal 
swim  in  one  direction  or  in  both? 

1.  Compare  the  body  with  that  of  a  lobster. 

2.  Are  appendages  present  on  each  of  the  divisions  of  the 
body  ?    Compare  them  with  the  appendages  of  the  lobster  ?    How 
do  the  thoracic  appendages  differ? 

3.  Notice  the  otocysts  in  the  tail  fin.     What  are  their  posi- 
tions? 

4.  The  living  animal  is  transparent,  and  many  internal  organs, 
such  as  heart,  gills,  and  portions  of  the  alimentary  canal,  can  be 
seen. 

//  time  permits,  make  a  drawing. 

Bergh:  Beitrage  zur  Embryologie  der  Crustacean.     Zool.  Jahr.  (Anat.), 
6,  1893. 

TALORCHESTIA.    (Beach-Flea.) 

These  active  little  animals  inhabit  sand  beaches,  where  they 
burrow  in  the  sand  and  hide  in  the  decaying  vegetable  matter 
that  accumulates  along  such  beaches  near  high-water  mark. 
Turn  over  some  of  this  material  and  notice  the  activity  of  the 
animals  that  are  disturbed.  Most  of  them  probably  belong  to 
another  closely  related  genus,  but  their  movements  are  much 
the  same.  How  far  can  a  specimen  leap?  Are  the  leaps  of  an 
individual  continuously  in  one  direction,  so  it  may  get  away 
from  the  point  of  danger?  Is  each  leap  straight  forward  or  does 
the  animal  whirl  in  the  air?  What  purpose  may  be  served  by 
the  leaping?  Try  to  catch  a  specimen.  Determine  how  the 
leaping  is  accomplished.  Determine  how  the  specimens  burrow. 

If  you  will  walk  along  a  beach  some  quiet  night  with  a  lan- 
tern you  will  probably  see  something  of  the  night  activities  of 
these  animals. 

1.  Select  a  large  specimen  and  count  the  number  of  segments. 
Is  the  body  divisible  into  head,  thorax,  and  abdomen? 


152  ABTHBOPODA. 

2.  The  eyes  are  not  stalked.     Are  they  compound? 

3.  The  second  antenna  of  the  male  are  very  large.    Compare 
them  with  the  first  antennae  and  with  the  antennae  of  a  female. 

4.  Around  the  mouth  are  the  labrum,  forming  an  upper  lip, 
the  first  maxillipeds  (fused),  forming  a  lower  lip,  and  between 
them  the  mandibles,  first  maxillce,  and  second  maxillce. 

5.  Examine  the  appendages  behind  the  mouth.    How  many 
are  there?    How  many  bear  claws?    Compare  these  claws  with 
those  of  a  lobster,  and  see  how  they  differ.     Which  appendages 
are  used  in  crawling?    Why  are  some  of  the  appendages  arranged 
so  they  can  be  twisted  around  by  the  sides  of  the  animal  ?    What 
are  the  remaining  appendages  used  for? 

6.  Spread  the  appendages  apart  and  find  the  gills,  which  are 
attached  to  the  bases  of  the  appendages. 
Make  a  drawing  of  the  animal. 

Small  wood:  The  Beach  Flea:  Talorchestia  longicornis.    Cold  Spring  Har- 
bor Monogr.,  1,  1903. 

PORCELLIO  OR  ONISCUS.    (Sow-Bug.> 

These  animals  occur  in  damp  places,  such  as  under  stones, 
logs,  etc.,  and  in  cellars.  They  live  for  the  most  part  on  decaying 
vegetable  matter.  To  what  class  of  the  Arthropoda  do  they  be- 
long? 

1.  Notice  the  shape.     Is  this  an  adaptation? 

2.  Is  the  body  divisible  into  head,  thorax,  and  abdomen? 
Count  the  number  of  segments.     Is  there  any  evidence  of  fusion 
at  the  posterior  end  of  the  body? 

3.  Examine  the  appendages. 

(a)  Are  the  eyes  stalked  or  sessile? 

(6)  Only  one  pair  of  antennae  is  present,  the  first  pair  being 
rudimentary. 

(c)  The  mouth  appendages  are  small.     They  consist  of  man- 
dibles, two  pairs  of  maxillce,  and  one  pair  of  maxillipeds. 

(d)  How  many  walking  legs  are  there?    Are  these  all  alike? 

(e)  Notice  the  character  and  number  of  the  abdominal  appen- 
dages.   On  the  posterior  surface  of  all  but  the  last  pair,  which 


CAPRELLA.   BRANCHIPUS.  153 

are  modified  to  form  anal  feelers,  are  gills.    These  are  the  only 
respiratory  organs.     Why  must  these  animals  live  in  damp  places  ? 
Make  a  drawing  of  the  animal  from  the  ventral  side. 

CAPRELLA. 

These  animals  are  very  common  on  hydroids,  but  because  of 
their  peculiar  shape  and  slow  motions  are  rather  inconspicuous. 
Watch  the  animals  and  see  how  they  move.  Is  the  body  kept 
at  rest  and  moved  by  the  action  of  the  appendages,  or  how  is 
movement  from  place  to  place  effected?  Are  the  appendages 
adapted  for  grasping?  Why  are  they  arranged  at  the  two  ends 
of  the  body?  Watch  specimens  and  see  if  you  can  determine 
on  what  they  feed 

The  form  is  of  interest  because  of  its  extreme  modification  to 
suit  it  to  the  needs  of  its  life.  There  is  some  difference  in  the 
structure  of  the  male  and  the  female.  The  adult  structure  does 
not  enable  us  to  determine  the  homology  of  appendages. 

1.  Count  the  segments  of  the  body.     Do  they  differ  in  num- 
ber and  shape  in  male  and  female  ?    The  first  represents  the  head 
with  two  fused  thoracic  segments.     The  abdomen  forms  a  mi- 
nute protuberance  at  the  posterior  end  of  the  body. 

2.  Examine  the  appendages. 

(a)  At  the  anterior  end  of  the  body  are  the  eyes,  two  pairs 
of  antennce,  a  pair  of  maxillipeds,  and  a  pair  of  legs. 

(b)  At  the  hinder  part  of  the  body  are  three  pairs  of  legs. 

(c)  Near  the  middle  of  the  body  of  the  female,  and  near  the 
anterior  end  in  the  male,  is  another  pair  of  legs. 

(d)  On  two  of  the  segments  which  do  not  bear  legs  are  gills. 
If  time  permits  make  a  drawing. 

BRANCHIPUS.    (Fairy  Shrimp.) 

These  animals  may  be  found  in  pools  of  fresh  water  in  the 
early  spring,  just  as  the  ice  is  leaving.  Their  method  of  swim- 
ming by  means  of  the  large,  expanded  appendages  should  be 
observed. 


154  ARTHROPODA. 

1.  Into  what  parts  does  the  body  seem  to  be  divided?    Do 
all  of  these  parts  show  segmentation? 

2.  Find  the  following  organs. 

(a)  The  stalked,  prominent  eyes. 

(b)  The  antennce.     In  the  female  the  first  are  slender  and 
the  second  vestigial.     In  the  male  the  first  are  slender  and  the 
second  are  enormously  enlarged  to  form  a  clasping  organ. 

(c)  The  labrum  (not  an  appendage)  forms  an  upper  lip. 

(d)  The  mandibles,  beneath  the  labrum  and  by  the  sides  of 
the  mouth.    Do  they  have  cutting-edges? 

(e)  Vestigial  maxillae  behind  the  mouth. 

(/)  Swimming  appendages.  How  many  are  there?  Notice 
the  fringe  of  hairs  on  each.  What  are  these  for?  Remove  one 
and  examine  it  with  a  microscope.  The  lobes  have  been  des- 
cribed as  exopodite  and  endopodite,  but  their  exact  relation- 
ship is  not  certain. 

A  drawing  is  desirable. 

DAPHNIA. 

This  small  fresh-water  form  frequently  occurs  in  large  num- 
bers in  small  pools  and  brooks.  Determine  how  it  swims.  Being 
small  and  transparent,  it  may  be  satisfactorily  studied  with  a 
compound  microscope. 

1.  Notice  the  shape  and  extent  of  the  protective  covering. 
To  what  part  of  other  crustaceans  does  this  correspond?    Are 
the  appendages  and  the  abdomen  capable  of  being  thrust  out? 
Are  there  any  signs  of  segmentation  of  the  body? 

2.  Determine  what  parts  are  used  in  keeping  a  current  of 
water  passing  through  the  shell.    Why  is  such  a  current  needed  ? 

3.  If  the  animal  carries  young,  notice  how  they  are  kept  in 
the  brood  chamber  by  a  spine  that  extends  up  from  the  dorsal 
portion  of  the  base  of  the  abdomen. 

4.  Notice  the  beating  of  the  heart. 

5.  Examine  the  appendages. 

(a)  Are  the  eyes  stalked  or  sessile?  They  frequently  show  a 
peculiar  reaction  to  light.  If  the  light  is  cut  off  from  the  micro- 


CYCLOPS. 


155 


scope,  the  eye  will  be  seen  to  rotate  on  its  axis.     If  the  light  is 
admitted  again,  the  eye  rotates  back  to  its  original  position. 

(b)  The  -first  antennce  are  very  small  and  project  ventrally. 
What  is  the  chief  function  of  the  second  antennae? 

(c)  Several  appendages  will  be  seen  inside  of  the  shell,  but 
it  is  hard  to  determine  their  exact  relation.    The  functions  of 
some  of  them  may  be  apparent. 

A  drawing  is  desirable. 

CYCLOPS.    (Water-Flea.) 

Most  any  free-swimming  copepod,  either  fresh-water  or  marine, 
will  answer  quite  as  well  as  the  fresh-water  Cyclops. 

Cyclops  may  be  found  in  almost  any  pool  of  fresh  water  and 
the  marine  forms  are  among  the  most  abundant  of  the  animals 
of  the  sea.  Surface  skimming  of  the  sea,  made  with  a  net  com- 
posed of  cheese-cloth  or  silk  bolting-cloth,  will  yield  an  abun- 
dance of  material. 

1.  Watch  the  animals  and  see  how  they  swim.    With   a 
pipet  try  to  catch  a  certain  individual  and  see  whether  the  jerky 
movements  probably  aid  these  animals  in  escaping  enemies. 
Determine  what  organs  are  used  in  swimming. 

2.  Examine  specimens  that  have  been  confined  under  a  cover- 
glass  with  a  microscope,  and  notice  the  shape  of  the  body. 
Into  what  parts  is  it  divided?     Count  the  number  of  segments. 
Look  for  evidence  of  fused  segments.     Notice  how  the  spines  on 
the  abdomen  are  arranged. 

3.  Examine  the  appendages. 

(a)  Do  you  find  eyes  that  are  equivalent  to  the  usual  arthro- 
pod eyes?    Do  you  find  an  eye-spot?    If  such  a  spot  is  found, 
determine  its  position  and  shape. 

(b)  Which  pair  of  antennce  is  largest?    Why  are  the  large 
antennce  fringed  with  spines? 

(c)  Are  there  thoracic  or  abdominal  appendages?    Are  any 
appendages  other  than  the  first  antennae  used  in  swimming? 

(d)  The  mouth  parts  consist  of  mandibles  and  two  maxilla. 

4.  If  the  specimen  is  a  female  it  may  have  two  large  egg  sacs 


156  ARTHROPODA. 

attached  to  the  sides  of  the  base  of  the  abdomen.  The  female 
has  two  of  the  abdominal  segments  fused.  In  the  male  the  seg- 
ments are  free. 

A  drawing  of  the  specimen  is  desirable. 

Sharper  Notes  on  the  Marine  Copepods  and  Cladocera  of  Woods  Hole  and 
Adjacent  Regions,  Including  a  Synopsis  of  the  Genera  of  the  Harpocti- 
coida.  Proc.  U.  S.  Nat.  Mus.,  38,  1910. 

Wheeler:  Free-Swimming  Copepods  of  the  Woods  Hole  Region.  Bui. 
U.  S.  Fish  Com.,  19,  1899. 

ARGULUS.    (Fish-Louse.) 

These  animals  may  be  found  on  many  species  of  fresh-water 
and  marine  fish.  Notice  their  shape  and  determine  how  they 
cling  to  their  host.  Are  they  able  to  crawl?  Can  they  swim? 

1.  Into  what  regions  can  the  body  be  divided? 

2.  Examine  the  appendages  and  find:  .  %< 

(a)  The   eyes,  the  eye-spot,   and  the  two    pairs    of   small 
antennce. 

(b)  The  sucking  proboscis,  composed  of  mandibles  and  max- 
illce,  which  lies  between  the  suckers. 

(c)  The  suckers,  which  are  the  modified  second  maxillce. 

(d)  The  posterior  (third)  maxillipeds  just  behind  the  suckers. 

(e)  Four  pairs  of  biramous  thoracic  appendages.     What  is 
their  function? 

Make  a  drawing  of  the  animal. 

Wilson:  The  Fish  Parasites  of  the  Genus  Argulus  Found  in  the  Woods  Hole 
Region.  Bui.  U.  S.  Bur.  Fish.,  24,  1904. 

LEPAS.    (Goose-Barnacle.) 

If  possible,  examine  a  cluster  of  specimens  as  they  naturally 
occur  attached  to  floating  timber. 

1.  Why  are  the  peduncles  much  larger  in  some  specimens 
than  in  others?    Are  they  contractile  so  the  body  may  be  moved 
into  different  positions?     Would  such  movements  be  of  value? 

2.  Notice  the  thoracic  appendages.     Can  they  be  thrust 
from  the  shell?    What  is  their  character?    What  are  their  char- 
acteristic movements?    Drop  a  small  piece  of  clam  meat  on 


LEPAS.  157 

these  appendages  of  a  living  specimen  and  see  what  happens. 
What  kind  of  food  would  they  naturally  collect  ? 

3.  Examine  the  portions  of  the  shell.     The  portion  on  the 
closed,  dorsal  margin  is  the  carina,  laterally  and  near  the  base 
of  the  peduncle  are  the  scuta,  and  near  the  extremity  the  terga. 
Why  are  there  so  many  pieces  ?    Notice  the  lines  of  growth  and 
determine  the  direction  of  growth  of  each  piece. 

Draw  the  animal  as  seen  from  one  side. 

With  a  scalpel  or  razor  cut  a  preserved  specimen  into  right 
and  left  halves,  extending  the  cut  through  the  peduncle. 

4.  The  mouth  will  be  seen  at  the  end  of  a  rather  thick  pro- 
longation which  is  extended  to  near  the  bases  of  the  abdominal 
appendages.     On  the  margin  of  this  prolongation  are  the  small 
scale-like  mandibles,  first  maxillce,  and  second  maxillce.     The  sto- 
mach is  rather  large  and  the%  small  intestine  leads  to  the  posterior 
end  of  the  abdomen,  where  it  opens  between  the  abdominal 
appendages. 

5.  The  nervous  system,  consisting  of  a  large  pair  of  cerebral 
ganglia  and  a  short  ventral  chain  of  ganglia,  should  be  seen  in 
such  a  section. 

6.  The  animal  is  hermaphroditic.    The  testes  lie  dorsal  to 
the  stomach  and  communicate  with  a  conspicuous  coiled  vas 
deferens  that  is  continued  to  the  elongated  penis  at  the  end  of  the 
abdomen.    What  reason  is  there  for  such  a  long  penis?    The 
ovary  occupies  the  interior  of  the  peduncle.     The  oviducts  are 
inconspicuous  and  hard  to  follow.    They  open  near  the  bases 
of  the  anterior  thoracic  appendages. 

7.  Examine  the  appendages  carefully  and  be  sure  that  you 
understand  the  relation  of  parts.    What  part  must  the  pedun- 
cle  represent?    Understand   the   beautiful   adaptation   of  the 
animal  for  its  life. 

A  drawing  showing  the  organs  is  desirable. 

Bigelow:  Early  Development  of  Lepas.     Bui.  Mus.  Comp.  Zool.  Harvard, 

40,  1902. 
Delage:  Evolution  de  la  Sacculine.     (Sacculina  carcini.)     Arch.  Zool.  Exp. 

et  Gen.,  2e  Series,  11,  1884. 


158  AKTHBOPODA. 


ARACHNOIDEA: 

LIMULUS.    (Horseshoe  Crab.) 

Notice  the  way  in  which  the  animal  crawls  upon  the  bottom. 
Is  it  well  protected  from  enemies?  Examine  it  carefully  for 
parasites  and  for  animals  that  are  attached  to  it.  Disturb  it 
and  see  if  it  will  swim.  The  animals  are  usually  quite  active 
in  the  evening,  and  if  you  visit  a  car  in  which  they  are  kept,  at 
this  time  of  the  day,  you  are  likely  to  find  them  crawling  up  the 
sides,  falling  over  and  swimming  on  their  backs.  In  this  posi- 
tion it  is  easy  to  determine  how  they  swim.  The  animals  are 
very  hardy  and  will  stand  even  complete  removal  from  the  water 
for  days  at  a  time.  During  the  spring  and  early  summer,  eggs 
are  deposited  in  the  sand;  the  male  holding  to  the  edge  of  the 
abdomen  of  the  female  with  claws  modified  for  the  purpose,  is 
dragged  after  her.  If  possible,  the  method  of  egg  deposition 
and  fertilization  should  be  observed. 

1.  The  animal  consists  of  a  hoof-shaped  cephalothorax,  an 
abdomen,  and  a  caudal  spine.    How  are  these  joined?    Is  there 
any  indication  of  segmentation  of  any  of  them? 

2.  Examine  the  eyes  with  a  lens  and  see  that  they  are  com- 
pound. -  \  &  6tt£  v  ? 

3.  On  the  lower  side  of  the  cephalothorax  notice  the  appen- 
dages.   Are  they  all  built  on  the  same  plan?    Compare  them  in 
male  and  female.     Do  you  know  what  the  modifications  are 
for?    Compare  the  pincers  with  those  of  a  lobster.    The  first 
pair  of  appendages  is  called  the  chelicerce.    Between  the  bases 
of  the  last  pair  of  walking  legs  are  the  chilaria.     Behind  the 
chilaria  is  the  operculum.    Does  this  show  evidence  of  being 
modified  appendages?    What  is  its  function? 

4.  Between  the  bases  of  the  cephalothoracic  appendages  is 
the  mouth.    Do  the  bases  of  the  appendages  show  any  modifi- 
cations that  may  serve  as  teeth?    Can  the  pincer-bearing  ap- 
pendages be  so  bent  as  to  be  used  in  feeding? 

5.  Along  the  sides  of  the  abdomen  notice  the  movable  spines. 
How  many  are  there?  6 


BUTHUS.  159 

6.  Under  the  operculum  are  the  gills.  How  many  groups 
are  there?  Are  they  arranged  in  pairs?  How  are  they  attached 
to  the  body?  Are  they  movable?  What  reason  is  there  for 
moving  them?  Examine  a  bunch  of  gills,  frequently  called  a 
gill-book,  and  see  how  it  is  formed. 

7.  At  the  base  of  the  caudal  spine  notice  the  anus. 

Make  a  drawing  of  the  ventral  surface. 

Internal  Anatomy. — This  shows  no  very  special  adaptation 
and  can  be  pretty  well  understood  by  studying  a  longitudinal 
section  of  a  small  preserved  specimen. 

In  such  a  section  the  following  organs  may  be  found: 

1.  The  dorsal  extensor,  the  ventral  flexor,  and  the  &#  muscles. 

2.  The  elongated  tubular  heart  just  beneath  the  dorsal  cover- 
ing, in  the  posterior  end  of  the  cephalothorax  and  the  anterior 
end  of  the  abdomen. 

3.  The  alimentary  canal,  consisting  of  the  esophagus  and  the 
anterior  and  posterior  portions  of  the  stomach,  which  extends 
posteriorly  without  much  change  to  the  anus.     The  liver,  which 
surrounds  the  stomach  and  fills  the  greater   portion  of    the 
cephalothorax,  sends  its  secretions  to  the  stomach. 

4.  The  cerebral  ganglia,  near  the  bases  of  the  chelicerse,  and 
the  ventral  chain  of  ganglia  should  also  be  seen  in  satisfactory 
sections. 

A  drawing  is  desirable. 

Lankester:  Limulus  an  Arachnid.     Quart.  Jour.  Mic.  Sci.,  21,  1881. 
Packard:   The  Anatomy,  Histology,  and  Embryology  of  Limulus  poly- 
phemus.     Mem.  Bost.  Soc.  Nat.  Hist.,  1880. 

BUTHUS.    (Scorpion.) 

Living  specimens  of  these  animals  are  not  usually  available 
for  laboratory  study.  They  live  for  the  most  part  concealed 
during  the  day  in  crevices  and  holes  and  are  active  at  night. 
Their  food  is  largely  spiders  and  insects  which  are  seized  by  the 
claws  and  killed  with  the  abdominal  sting. 

1.  Into  what  parts  is  the  body  divided?  How  many  seg- 
ments are  recognizable?  Which  are  the  most  freely  movable? 


160  ARTHKOPODA. 

2.  Look  for  eyes.    Do  you  find  any  besides  the  large  pair? 

3.  Find  four  pairs  of  slit-like  openings  on  the  ventral  side  of 
the  pre-abdomen.    These  are  the  stigmata,  the  openings  of  the 
lung-books. 

4.  Find  the  following  appendages: 

(a)  The  chelicerce.  What  is  their  structure  and  where  are 
they  placed? 

(6)  The  pedipalpi.  Compare  them  with  the  chelicerse  and 
count  their  segments. 

(c)  Four  pairs  of  walking  legs.    Count  their  segments  and  see 
if  they  are  armed  with  claws. 

(d)  The  comb-shaped  pectines.    Are  they  on  the  thorax  or 
the  abdomen?    Their  function  is  doubtful,      x^  i«  u 

5.  Examine  the  mouth.    Are  there  any  jaws?    Is  a  labrum 
present? 

6.  Find  the  position  of  the  anus.    The  terminal  spine  is  pro- 
vided with  a  poison  gland  and  serves  as  a  sting.    In  the  living 
animal,  the  post-abdomen  is  habitually  carried  over  the  back. 

Make  a  drawing  of  the  under  side  of  a  specimen. 

EPEIRA.    (Round-Web  Spider.) 

Examine  the  webs  of  different  species  of  spiders  and  see  how 
they  are  constructed.  Do  all  of  the  webs  have  places  for  the 
concealment  of  the  owners?  Do  all  spiders  seem  to  construct 
definite  webs  for  the  capture  of  insects?  How  do  spiders  entan- 
gle insects  in  their  webs?  Do  different  kinds  use  different 
methods?  What  parts  of  insects  are  eaten? 

By  destroying  webs  that  are  occupied  by  spiders  that  are  in 
convenient  places  for  observation,  the  construction  of  new  webs 
may  be  observed.  Notice  how  the  framework  is  laid  and  then 
how  the  threads  are  attached  to  the  framework.  Are  any  of 
the  legs  used  in  handling  the  thread  ?  Are  spiders  equally  active 
at  all  times  of  the  day  ? 

Spiders'  webs  may  frequently  be  seen  floating  in  the  air, 
especially  in  the  late  summer  or  autumn.  By  watching  spiders 
that  are  on  fences  and  bushes  the  formation  of  these  threads 


EPEIRA.  161 

may  be  observed.  Watch  such  a  spider  and  see  if  you  can  deter- 
mine the  use  to  which  the  thread  is  put. 

Capture  a  spider  and  watch  it  descend  by  a  thread.  Where 
is  the  thread  formed?  Does  the  spider  hold  to  it  with  its  legs? 
Keep  taking  the  thread  up  so  that  the  spider  cannot  reach  the 
ground,  and  see  if  there  is  a  limit  to  the  amount  that  can  be 
formed.  When  the  spider  starts  to  climb  the  thread  see  how 
this  is  done,  and  whether  the  thread  is  taken  up  as  the  animal 
climbs  or  is  allowed  to  float  free. 

Find  where  spiders  lay  their  eggs.  Some  carry  them.  If 
you  can  find  a  specimen  with  an  egg-sac,  see  how  it  is  carried 
and  whether  it  will  drop  its  eggs  when  frightened.  Remove  the 
egg-sac  and  see  if  the  spider  will  accept  it  again.  Open  several 
egg-sacs  and  see  if  the  eggs  all  appear  to  be  in  the  same  stage 
of  development. 

Study  the  movements  of  the  animal  and  see  how  many  of 
the  appendages  are  used  in  locomotion.  Are  any  of  the  appen- 
dages used  sometimes  for  locomotion  and  sometimes  for  feel- 
ing? 

Examine  the  external  structure  of  Epeira. 

1.  Into  what  parts  is  the  body  divided?    Do  both  parts  bear 
appendages? 

2.  Look  for  eyes  on  the  anterior  end  of  the  body.    How 
many  are  there?    Do  they  seem  to  be  simple  or  compound? 
Determine  whether  a  specimen  can  see. 

3.  The  following  appendages  should  be  found: 

(a)  The  chelicerce  or  mandibles.  Notice  their  structure  and 
see  that  each  ends  in  a  sharp  claw.  The  poison-gland  discharges 
at  the  tip  of  this  claw. 

(6)  The  pedipalpi  or  palpi.  How  many  segments  have 
they?  Examine  their  tips  for  claws.  What  are  they  appar- 
ently used  for? 

(c)  Four  pairs  of  legs.    Are  they  all  alike?    Count  the  seg- 
ments and  examine  their  tips  for  claws. 

(d)  On  the  abdomen,  three  pairs  of  spinnerets.     Notice  their 
positions  and  see  if  they  are  segmented.    Understand  their  func- 

11 


162  ARTHROPODA. 

tion  and  whether  they  are  all  used  at  the  same  time.     They 
are  probably  true  abdominal  appendages. 

4.  On  the  lower  surface  of  the  abdomen,  near  its  anterior 
end,  are  two  slits,  the  openings  into  the  lung-sacs  or  lung-books. 
They  are  respiratory  in  function. 

5.  Just  in  front  of  the  spinnerets  is  a  minute  median  pore, 
the  spiracle,  that  is  often  very  hard  to  find.     It  is  the  external 
opening  of  a  series  of  abdominal  tracheae. 

Make  a  drawing  of  a  ventral  view. 

Montgomery:  Studies  on  the  Habits  of  Spiders,  Particularly  Those  of  the 

Mating  Period.     Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1903. 
:  On  the  Spinnerets,  Cribellum,  Colulus,  Tracheae  and  Lung-books  of 

Araneads.     Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1909. 
:  The  Development  of  Theridium,  an  Aranead,  up  to  the  Stage  of 

Reversion.     Jour.  Morph.,  20,  1909. 
:  The  Significance  of  the  Courtship  and  Secondary  Sexual  Characters 

of  Araneads.     Am.  Nat.,  44,  1910. 
Peckham:  Observations  on  Sexual  Selection  in  Spiders  of  the  Family  At- 

tidse.     Occas.  Papers  Nat.  Hist.  Soc.,  Wisconsin,  1  and  2. 


PHOXICHILIDIUM. 

The  exact  affinities  of  the  pygnogonids  to  other  forms  is 
not  known,  but  they  have  certain  characters  that  have  suggested 
a  possible  relationship  to  the  Arachnoidea.  They  are  frequently 
found  in  considerable  abundance  on  the  material  that  is  attached 
to  piles.  Notice  their  movements  and  see  how  they  cling  to  the 
material  on  which  they  are  moving. 

1.  The  body  is  very  slender  and  is  composed  of  a  number  of 
free  segments  that  form  the  head  and  thorax  and  a  small,  ves- 
tigial abdomen.    How  many  free  segments  are  there?    At  the 
anterior  end  is  a  rather  prominent  proboscis,  with  the  mouth  at 
its  end. 

2.  The  following  appendages  will  be  found: 

(a)  The  chelicerce.  What  is  their  structure?  Are  they 
armed  with  pincers? 

(6)  Four  pairs  of  long  walking  legs.  How  many  segments 
have  they?  The  viscera  extends  into  the  bases  of  these  appen- 
dages. 


LITHOBIUS.  163 

(c)  The  male  is  provided  with  a  pair  of  ventral  appendages 
called  the  ovigerous  legs,  by  means  of  which  the  eggs  are  collected 
as  they  are  laid  by  the  female.  These  appendages  are  not  present 
in  the  female. 

Make  a  drawing  of  the  under  side  of  a  specimen. 

Cole:  Pycnogonidia  of  the  West  Coast  of  North  America.     Harriman 
Alaska  Exped.,  10,  1904. 


MYRIAPODA; 

LITHOBIUS.    (Centipede,  Earwig.) 

These  animals  may  frequently  be  found  under  stones,  logs 
or  boards,  or  about  rubbish  or  manure  heaps.  They  live  largely 
on  insects,  larvae,  and  small  worms,  and  are  very  active. 

1.  Notice  the  shape  of  the  body  and  count  the  number  of 
segments.     Is  there  a  distinct  head?    Are  the  segments  very 
movable  ? 

2.  How  many  appendages  does  each  segment  possess?    Are 
all  of  the  segments  provided  with  appendages?     Allow  the  ani- 
mal to  run  and  see  how  the  legs  are  used.    Do  those  of  a  side  all 
move  in  the  same  direction  at  the  same  time?    Are  all  of  the 
legs  alike?    Notice  the  pair  of  appendages  just  behind  the  head 
and  see  how  they  differ  from  the  others.    These  appendages  are 
organs  of  prehension  that  are  used  in  grasping  the  prey.     They 
are  provided  with  poison  glands  that  open  on  their  inner  sides 
near  their  free  ends. 

3.  Examine  the  head  and  find  the  eyes,  antenna,  and  mouth 
parts.     The  latter  consist  of  a  labrum,  a  pair  of  mandibles,  and 
two  pairs  of  maxillce,  the  last  pair  of  which  are  united  to  form  a 
labium. 

4.  Understand  how  the  animal  breathes.    The  stigmata  are 
situated  near  the  bases  of  the  legs,  but  are  hard  to  see  except  in 
favorable  specimens. 

Make  a  drawing  of  the  animal. 


164  ARTHROPODA. 


JULUS.    (Thoaaand-iegB.) 

These  animals  are  frequently  very  abundant  under  the  dead 
bark  of  logs  or  stumps,  in  decaying  wood,  and  in  decaying  heaps 
of  grass.  In  the  autumn  they  frequently  congregate  under 
boards  and  in  corners.  They  feed  on  decaying  vegetable  matter. 

1.  Disturb  a  specimen  and  see  how  it  rolls  up.     Can  this 
be  protective?    See  if  there  is  any  odor  when  it  is  disturbed. 
What  purpose  can  such  an  odor  serve? 

2.  What  is  the  shape  of  the  body?    Is  it  hard  or  soft?    How 
many  segments  are  there? 

3.  How  many  appendages  are  borne  on  a  segment?    Do  all 
of   the   segments  bear   appendages?    Does   the   animal   move 
rapidly?     Why  does  it  not  need  to  move  as  rapidly  as  the  pre- 
ceding form?    Do  the  first  pair  of  appendages  behind  the  head 
show  modifications  for  prehension?    Does  this  animal  need  such 
an  organ? 

4.  Compare  the  organs  of  the  head  with  those  of  the  preced- 
ing form. 

Make  a  drawing  of  the  under  side  of  one  segment. 

Williams:  Habits  and  Structure  of  Scutigerella  immaculata.     Proc.  Bost. 
Soc.  Nat.  Hist.,  33,  1907. 


INSECTA; 

ACRIDIUM.    (Grasshopper.) 

Study  grasshoppers  as  they  occur  in  nature  and  determine 
as  far  as  possible  the  following  points: 

1.  Do  they  see  or  hear?    Are  they  equally  sensitive  to  touch 
on  all  parts  of  the  body?    Why  should  the  animal  be  well  pro- 
vided with  sense  organs? 

2.  What  is  their  food?    Are  all  plants  eaten  or  are  some 
avoided  ?    See  how  the  mouth  parts  are  used  in  feeding. 

3.  What  are  the  important  enemies  of  grasshoppers?    How 
do  they  escape  their  enemies?    Do  they  hide?    Are  they  pro- 
tectively colored?    How  does  jumping  serve  them  better  than 


ACRlDItTM.  165 

( 

crawling?  How  many  times  its  length  can  a  grasshopper  jump? 
Why  are  wings  needed? 

4.  During  late  summer  and  autumn  you  may  find  individuals 
depositing  eggs.  See  if  you  can  determine  how  the  end  of  the 
body  is  worked  into  the  ground. 

For  study  it  is  desirable  to  use  a  rather  large,  freshly  killed 
or  alcoholic  specimen. 

The  body  is  divided  into  three  well-marked  regions. 

1.  The  Head. — Is  it  movable?    Does  it  need  to  be  as  mova- 
ble as  your  own  head  ?    It  bears  several  organs. 

(a)  The  compound  eyes.  Examine  one  with  a  lens  or  remove 
its  outer  covering  and  examine  it  with  a  compound  microscope. 
You  should  understand  the  structure  of  the  whole  eye  and  how 
it  gives  a  single  visual  image. 

(&)  The  ocelli,  three  in  number,  one  near  the  middle  of  the 
front  part  of  the  head  and  the  others  placed  near  the  bases  of 
the  antennae. 

(c)  The  antennce.    Why  are  they  so  flexible?    Examine  one 
with  a  microscope  and  notice  the  spines.     What  are  these  for? 

(d)  Mouth  parts.    These  should  be  studied  later. 

2.  The  Thorax. — Why  should  it  be  large  and  comparatively 
firm?.   This  portion  is  more  or  less  distinctly  divided  into  three 
parts,  each  of  which  carries  a  pair  of  legs. 

(a)  Compare  the  three  legs  of  one  side.  Do  they  have  the 
same  number  of  segments?  Do  all  of  the  joints  of  the  leg  move 
in  the  same  plane?  The  five  divisions  of  a  leg  are,  beginning 
with  the  basal  end:  coxa,  trochanter  (immovably  joined  to  the 
coxa  in  the  leaping  legs),  femur,  tibia,  and  tarsus,  which  is  com- 
posed of  four  movable  pieces.  Why  do  the  femurs  of  the  leap- 
ing legs  differ  from  the  femurs  of  the  other  legs?  Determine 
how  the  foot  is  arranged  to  hold  to  objects.  Have  you  noticed 
a  grasshopper  settle  its  feet  preparatory  to  jumping?  Examine 
the  joint  between  the  femur  and  tibia. 

(6)  Examine  the  wings  and  notice  their  size,  shape,  places 
of  attachment,  and  general  character.  Do  they  apparently 
have  different  functions  to  perform?  Notice  how  the  posterior 


166  [ARTHROPODA. 

wings  are  folded  so  they  may  be  covered  by  the  anterior.  Does 
this  seem  to  greatly  reduce  their  strength?1 

3.  The  Abdomen. — Count  the  number  of  segments.  Each 
one  is  covered  dorsally  by  a  tergum  and  ventrally  by  a  sternum. 
Why  should  the  abdomen  be  more  movable  than  the  other  por- 
tions? The  posterior  ends  of  the  abdomens  of  male  and  female 
differ.  This  portion  of  the  female  is  modified  to  form  the  ovi- 
positor, which  consists  of  two  large  pairs  of  plates  that  inclose 
a  smaller  pair  of  plates.  It  is  between  these  plates  that  the 
oviduct  opens.  Why  do  the  larger  plates  possess  hard  tips? 
Along  the  sides  of  the  abdomen  notice  the  stigmata,  the  external 
openings  of  the  respiratory  system.  Do  you  find  stigmata  on 
other  parts  of  the  body? 

Draw  an  enlarged  side  view  of  a  grasshopper,  placing  the  appen- 
dages in  their  proper  positions. 

Mouth  Parts. — It  has  already  been  noticed  that  the  mouth 
parts  serve  to  cut  off  pieces  of  leaves,  which  are  then  passed 
directly  into  the  alimentary  canal.  For  such  a  purpose  there 
should  be  holding  as  well  as  cutting  parts. 

1.  Pass  a  needle  under  the  labrum,  which  forms  the  upper 
lip,  and  notice  that  it  is  hinged  and  that  the  end  is  lobed.     It  is 
not  supposed  to  be  homologous  with  usual  arthropod  appendages. 
With  fine  scissors  remove  it  and  place  it  in  a  watch-glass  contain- 
ing water. 

2.  Immediately  behind  the  labrum  is  a  pair  of  hard,  dark- 
colored  organs,  the  mandibles,  that  are  used  in  cutting  the  food. 
Their  position  should  be  carefully  noted,  but  it  will  be  better 
to  leave  them  in  position  until  the  other  mouth  appendages 
have  been  removed. 

3.  Situated  by  the  side  of  the  mouth  and  just  behind  the 
mandibles  are  the  maxillce.    With  a  needle  push  one  to  one  side 
and  notice  that  it  consists  of  a  somewhat  flattened  portion  with 
a  jointed  maxillary  palp  at  one  side.     Carefully  determine  the 
positions  of  the  maxillae  with  relation  to  other  parts.     What 
possible  uses  are  served  by  the  two  parts?    Remove  them  with 

1  You  should  examine  the  posterior  wing  of  a  beetle  and  see  how  it 
is  folded. 


ACKIDIUM.  167 

scissors  and  place  them  in  the  watch-glass  with  the  labrum,  in 
approximately  their  relative  positions  and  study  carefully. 

4.  Pass  a  needle  behind  the  remaining  appendage,  the  Idbium, 
and  see  that  it  is  hinged  and  forms  the  lower  lip.     Remove  it 
with  scissors  and  place  it  in  position  hi  the  watch-glass.    You 
will  find  that  it  bears  a  pair  of  labial  palpi,  and  that  there  is  a 
deep  cleft  along  the  middle  line.    These  are  indications  that  the 
appendage  is  the  result  of  the  fusion  of  a  pair  of  appendages. 

5.  Remove  the  mandibles  and  examine  their  cutting  margins. 
Place  them  in  position  in  the  watch-glass. 

Make  a  drawing  showing  the  structure  of  each  of  these  appen- 
dages. Arrange  your  figures  as  nearly  as  possible  in  the  relative 
positions  of  the  parts.1 

Internal  Structure. — Remove  the  wings,  and  before  opening 
the  body  notice  the  rather  large,  somewhat  transparent  tympa- 
num on  each  side  of  the  first  abdominal  segment,  very  near  the 
base  of  the  leaping  leg.  The  structure  of  the  auditory  organ 
may  be  easily  studied  by  staining,  clearing,  and  mounting  in 
balsam.  (See  Packard's  "Text-Book  of  Entomology"  or 
Brooks's  "Hand-book  of  Invertebrate  Zoology.")  Remove  the 
dorsal  portion  of  the  wall  of  the  abdomen  and  thorax,  and  notice: 

1.  The  heart,  which  will  be  found  attached  to  the  portion  of 
the  wall  of  the  abdomen  that  has  been  removed,  by  means  of 
numerous  radiating  muscle  fibers.     You  probably  will  not  be 
able  to  determine  the  structure  of  the  heart  in  the  dissection. 
Read  this  up,  and  determine  what  the  radiating  muscle  fibers 
are  for. 

2.  The  space  between  the  muscles  and  the  viscera  is  filled 
more  or  less  completely  by  the  fat-body  and  the  trachece.     With 
a  lens  notice  how  the  tracheae  connect  with  the  spiracles  and 
how  they  branch.      Remove  a  portion  of  the  tissue  in  which 
you  can  see  tracheae,   mount  it  in  water  under  a  cover,  and 
examine  it  microscopically.     Each  tracheal  tube  is  marked  by 

1The  mouth  parts  of  all  insects  that  depend  on  biting  off  portions 
of  plants  for  food  are  quite  similar.  Directions  for  the  study  of  the 
mouth  parts  of  the  honey-bee  are  given  further  on,  but  the  mouth  parts 
of  other  forms,  such  as  the  fly,  butterfly,  and  bug,  should  be  studied. 


168  ARTHROPODA. 

striations  wound  around  it.  Do  you  know  what  causes  this 
appearance  and  what  the  arrangement  is  for?  Do  you  under- 
stand how  the  tracheal  system  is  arranged  ?  Why  is  it  extended 
all  over  the  body  and  how  is  the  air  made  to  go  in  and  out? 

3.  Near  the  dorsal  surface  of  the  posterior  part  of  the  ab- 
domen, surrounded  by  the  tissues  already  mentioned,  are  the 
gonads.    These  differ  in  size  and  shape  according  to  the  sex.    In 
the  male  the  vasa  deferentia  may  be  seen  leaving  the  lobulated 
testes.     In  the  female  the  oviducts  pass  around  the  sides  of  the 
intestine.    They  may  be  followed  later. 

4.  Loosen  the  anterior  ends  of  the  gonads  and  turn  them 
posteriorly  to  expose  the  hinder  part  of  the  alimentary  canal.1 

(a)  The  esophagus,  which  bends  backward  from  the  mouth, 
gradually  enlarges  as  it  enters  the  thorax. 

(6)  The  crop,  which  is  not  sharply  separated  from  the  esoph- 
agus, gradually  narrows  posteriorly. 

(c)  Following  the  constriction  posterior  to  the  crop  is  the 
elongated  stomach,  frequently  called  the  ventriculus.     Surround- 
ing the  anterior  end  of  this  portion  are  a  series  of  rather  large 
diverticula,  the  gastric  cceca,  that  extend  both  anteriorly  and 
posteriorly  from  the  points  where  they  open  into  the  stomach. 

(d)  Some  distance  behind  the  posterior  ends  of  the  hepatic 
caeca,  quite  concealed  by  the  mass  of  small  uriniferous  tubes,  is  a 
slight  constriction  and  hardening  of  the  alimentary  canal  that 
marks  the  division  between  the  stomach  and  intestine.    It  is  at 
this  point  that  the  uriniferous  tubes  join  the  alimentary  canal. 

(e)  Behind  the  intestine  the  alimentary  canal  becomes  much 
smaller  and  is  known  as  the  hind  intestine  or  colon. 

(/)  Behind  the  colon,  forming  the  hinder  portion  of  the  ali- 
mentary canal,  is  the  slightly  enlarged  rectum.  The  rectum 
cannot  be  seen  until  the  ovary  is  removed,  which  should  be  de- 
ferred until  the  ducts  have  been  seen. 

Make  a  drawing  showing  the  position  of  the  parts  of  the  alimen- 
tary canal  in  side  view. 

1  There  is  great  diversity  in  the  parts  of  the  alimentary  canals  of 
different  insects.  The  great  differences  in  feeding  habits  render  this 
necessary. 


ACBIDIUM.  169 

Cut  the  intestine  and  turn  the  alimentary  canal  posteriorly 
and  anteriorly. 

5.  Notice  the  muscles: 

(a)  That  move  the  abdominal  segments. 

(6)  That  move  the  legs  (those  that  supply  the  wings  have 
been  destroyed). 

(c)  That  move  the  jaws. 

Do  you  understand  now  why  the  thorax  needs  to  be  compar- 
atively large  and  firm? 

6.  The  nervous  system  is  directly  comparable  to  that  of  the 
lobster,  but  the  connectives  between  the  ganglia  will  be  found 
to  be  distinctly  double  and  the  ganglia  to  be  somewhat  differently 
arranged.1 

The  ventral  chain  will  be  found  to  consist  of  a  pair  of  sub- 
esophageal,  three  pairs  of  thoracic,  and  five  pairs  of  abdominal 
ganglia  with  the  connectives  between  them.  Which  of  these 
are  largest?  Why  is  this  the  case?  Trace  the  nerves  from  them 
and  see  what  organs  they  supply. 

Trace  the  connectives  forward  from  the  sub-esophageal  ganglia 
and  see  that  they  pass  around  the  esophagus,  thus  forming 
the  circum-esophageal  connectives.  Cut  away  the  dorsal  portion 
of  the  head  and  expose  the  cerebral  ganglia. 

Add  the  nervous  system  to  the  figure  that  shows  the  alimentary 
canal. 

7.  Trace  the  oviducts  down  around  the  sides  of  the  body 
and  notice  that  they  unite  with  each  other  ventral  to  the  nervous 
system,  to  form  the  vagina.     This  may  be  traced  to  its  opening 
between  the  plates  of  the  ovipositor.    Dorsal  to  the  vagina, 
opening  to  the  exterior  very  near  it,  is  a  small  sac,  the  sperma- 
theca,  which  serves  to  store  the  spermatozoa  received  from 
the  male  until  the  eggs  are  laid. 

The  reproductive  organs  may  also  be  added  to  your  figure  show- 
ing internal  anatomy. 

Brooks:  Hand-book  of  Invertebrate  Zoology. 

1  The  arrangement  of  the  ganglia  in  insects  is  very  variable,  showing 
many  gradations  in  concentration. 


170  ARTHBOPODA. 


APIS  MELLIFICA.    (Honey-B«e.) 

The  life  of  this  form  is  so  different  from  that  of  the  grasshopper 
that,  should  time  permit,  a  study  of  its  complete  anatomy  would 
be  profitable,  but  attention  will  here  be  confined  to  a  few  of  the 
more  general  adaptations  that  fit  it  for  its  life. 

Bees  at  work  on  flowers  should  be  examined  and  the  methods 
of  getting  honey  and  pollen  noticed. 

1.  Catch  by  the  wings  a  bee  that  has  been  gorging  itself 
and  bend  the  abdomen  forward  with  your  thumb-nail  until  the 
bee  disgorges.     Notice  where  the  fluid  comes  from  and  how 
much  there  is  of  it.     When  the  abdomen  is  released  watch  the 
bee  as  it  swallows  the  drop  it  has  disgorged. 

2.  Notice  where  the  pollen  is  carried,  and  see  if  you  can  de- 
termine how  it  is  attached.    Examine  bees  working  on  different 
flowers,  or  watch  them  as  they  enter  their  hives,  and  see  if  the 
pollen  is  always  of  the  same  color.     Do  you  understand  what 
the  pollen  is  and  what  the  bees  use  it  for? 

3.  You  may  find  bees  gathering  pitch  from  buds,  knots, 
boards,  or  freshly  varnished  furniture,  and  fastening  it  on  their 
legs.    Do  you  know  what  this  is  used  for? 

4.  Watch  the  entrance  of  a  bee-hive  and  see  if  those  going 
in  are  ever  challenged.     Perhaps  you  may  see  the  method  of 
defense.     If  so,  you  will  notice  that  the  stranger  simply  tries 
to  get  away.     You  may  also  see  how  dead  bees  and  foreign  ma- 
terials are  removed. 

5.  It  is  desirable  to  see  something  of  the  activities  in  the  hive. 
This  can  be  most  satisfactorily  done  with  an  observatory  hive, 
by  means  of  which  comb-building,  honey-storing,  egg-laying, 
brood-rearing,  etc.,  can  be  very  satisfactorily  studied. 

Directions  for  the  study  of  the  mouth  parts  and  the  sting  are 
all  that  seem  necessary,  but  the  wings  should  be  examined 
microscopically  to  see  how  those  of  a  side  are  joined  together, 
and  a  hind-leg  should  be  examined  to  see  how  the  hairs  on  the 
tibia  form  a  pollen  basket. 

Mouth  Parts. — 1.  With  a  lens  notice  that  there  is  a  pair  of 


APIS   MELLIFICA.  171 

hard  jaws,  the  mandibles,  situated  on  the  sides  of  the  head  at 
the  base  of  the  tongue.  These  mandibles  are  directly  homolo- 
gous with  the  mandibles  of  the  grasshopper.  Between  the  bases 
of  the  mandibles  is  a  labrum,  and  extending  from  beneath  the 
end  of  the  labrum  is  a  small  epipharynx. 

2.  With  scissors  remove  the  tongue,  which  is  normally  carried 
against  the  lower  surface  of  the  thorax,  and  transfer  it  to  a 
watch-glass.     It  may  now  be  dehydrated,  passed  into  oil  of 
cloves,  placed  in  position  on  a  slide,  and  mounted  in  balsam, 
when  it  can  be  studied  best,  or  it  may  be  immediately  spread 
under  a  cover  or  between  slides  in  glycerin. 

3.  The  central  portion  is  the  hairy,  segmented  labium  (the 
hypopharynx  of  some  authors),  bearing  at  its  end  a  little  pad 
called  the  spoon.    The  labium  is  folded  lengthwise  so  as  to  form 
a  pair  of  fine  ducts  which  run  from  tip  to  base.    The  arrange- 
ment is  such  that  the  bee  may,  through  blood-pressure,  unfold 
the  labium.    This  probably  is  an    adaptation  for  cleaning  it. 
Attached  to  a  median  rod,  the  mentum,  which  forms  the  base 
of  the  labium,  is  a  pair  of  flattened  appendages,  the  labial  palps, 
that  are  hinged  so  that  they  may  be  drawn  together  to  inclose 
the  labium  and  thus  form  a  rather  large  tube,  which  is  made 
more  complete  by  means  of  the  remaining  pair  of  flattened 
appendages,  the  maxillce.    On  the  outer  margin  of  each  maxilla 
is  a  small  protuberance,  the  maxillary  palp.    When  sipping 
from  an  abundance  of  liquid  the  extemporized  tube  formed  by 
the  labial  palps  and  maxillae  around  the  labium  is  used,  the 
liquid  being  drawn  in  by  means  of  the  sucking  stomach.     When 
the  liquid  is  in  very  small  quantities  it  is  apparently  lapped  up 
by  the  spoon  and  transferred  through  the  labium.1 

A  figure  of  the  mouth  parts  is  desirable. 

Sting. — The  sting  is  to  be  regarded  as  a  modified  ovipositor 
that  is  no  longer  concerned  in  depositing  eggs,  but  has  become 
a  weapon  of  offense  and  defense.  It  is  accordingly  present  only 

1  The  comparative  study  of  the  mouth  parts  of  a  butterfly,  horse-fly, 
house-fly,  and  mosquito  will  prove  valuable. 


172  ARTHROPODA. 

in  the  female.  The  queen  never  uses  her  sting  except  in  com- 
bat with  other  queens. 

Remove  the  dorsal  integument  of  the  abdomen  of  either  a 
fresh  or  preserved  specimen,  and  find  the  dark  brown  shaft  of 
the  sting,  near  the  posterior  end.  Grasp  the  shaft  with  a  pair 
of  fine  forceps  and  forcibly  remove  it.  A  considerable  mass  of 
tissue  will  be  removed  adhering  to  the  base  of  the  shaft,  but  this 
consists  for  the  most  part  of  accessory  organs  that  must  be 
understood.  Spread  the  sting  upon  a  slide,  and  either  dehy- 
drate and  mount  in  balsam,  or  mount  in  glycerin.  The  balsam 
mount  will  prove  more  satisfactory,  but  the  cover  must  be 
clamped  down  until  the  balsam  hardens. 

1.  The  shaft  consists  of  three  parts: 

(a)  A  heavy  support,  called  the  awl  or  sheath,  pointed  at  its 
extremity  and  sending  a  pair  of  arms  or  arches  from  its  base, 
which  normally  bend  ventrally,  but  are  here  forced  to  the  sides. 
At  its  extremity  each  of  these  arches  enlarges  to  form  a  rather 
large  flattened  plate,  the  sheath  plate,  to  which  strong  muscles 
are  attached. 

(b)  A  pair  of  lancets  which  are  fastened  to  the  dorsal  surface 
of  the  sheath  and  the  sheath  arches  by  tongue  and  groove  joints 
(each  tongue  is  enlarged  along  its  inner  margin  so  that  it  is  held 
firmly  in  the  groove).    Each  lancet  is  pointed  at  its  free  extrem- 
ity, and  its  sides  near  the  point  are  set  with  barbs  that  point 
toward  the  base  of  the  sting.    The  arch  of  each  lancet  is  con- 
tinued past  the  end  of  the  corresponding  sheath  arch,  and  is 
there  articulated  to  one  corner  of  a  somewhat  triangular  plate. 
The  remaining  corners  of  each  are  articulated  respectively  to  the 
large  sheath  plate  and  to  another  plate,  the  oval  plate.    Deter- 
mine the  attachment  of  the  muscles  to  the  plates  and  find  what 
movements  of  the  lancet  the  contraction  of  the  different  sets  of 
muscles  would  cause.    You  must  understand  that  the  lancets 
are  elastic  and  bend  quite  easily. 

The  large  muscles  attached  to  the  sheath  plates  were  attached 
to  the  wall  of  the  abdomen  and  function  to  give  the  thrust  that 
sets  the  sting.  After  the  sting  is  drawn  from  the  body  of  the  bee. 


APIS   MELLIFICA.  173 

the  muscles  attached  to  the  plates  continue  active,  and  the  sting 
works  deeper  and  deeper  in.  Understand  why  it  works  in  instead 
of  out. 

2.  Lying  near  the  base  of  the  shaft  is  a  large  poison  sac  or 
reservoir,  which  is  very  muscular.     It  receives  its  poison  from 
the  poison  gland,  a  long  and  narrow  coiled  tube  that  is  bifurcated 
near  its  free  end.     It  discharges  the  poison  by  means  of  the 
contraction  of  the  muscles  of  its  walls  through  a  rather  large, 
short  duct  into  the  space  inclosed  by  the  sheath  and  the  two 
barbs.    Each  barb  bears  a  prominence  that  serves  as  an  injector, 
which  moves  backward  and  forward  with  the  barb  to  which  it 
is  attached,  in  an  enlargement  of  the  basal  portion  of  the  sheath. 
It  may  be  seen  in  the  preparation.     In  this  way  poison  is  forced 
into  the  wound.    Poison  may  also  be  admitted  to  the  cavities 
of  the  lancets,  which  are  hollow,  and  escape  through  minute  pores 
near  the  barbs. 

3.  Lying  near  the  base  of  the  shaft  of  the  sting,  sometimes 
covered  by  the  poison  sac,  may  nearly  always  be  found  the  last 
pair  of  abdominal  ganglia,  from  which  nerves  may  be  traced  to 
the  muscles  that  are  attached  to  the  plates. 

Understand  the  whole  mechanism,  how  it  is  operated  and 
its  use. 

4.  Catch  a  living  bee  by  the  wings  and  press  the  end  of  the 
abdomen  against  a  piece  of  soft  leather,  such  as  a  leather-covered 
book.     Pull  the  bee  away  and  with  a  lens  watch  the  movements 
of  the  sting,  which  will  remain  in  the  leather.     Observe  the 
spasmodic  contractions  of  the  poison  sac.     See  how  long  and  how 
energetically  the  movements  are  continued  and  how  deep  the 
sting  is  worked  in.     This  should  remind  you  that  a  sting  should 
be  removed  immediately,  and  that  it  should  not  be  pulled  out, 
as  grasping  the  poison  sac  will  aid  in  injecting  the  poison,  but 
scraped  off  with  a  finger-nail  or  some  other  instrument. 

A  drawing  showing  the  mechanism  of  the  sting  is  desirable. 

Field:  A  Study  of  an  Ant.     Proc.  Acad.  Nat.  Sci.,  Philadelphia,  1901. 
Phillips:  A  Review  of  Parthenogenesis.     Proc.  Am.  Phil.  Soc.,  42,  1903. 
Root:  A,  B,  C,  and  X,  Y,  Z,  of  Bee  Culture. 


CHORDATA. 

With  notochord,  dorsal  nerve  cord,  and  branchial  clefts  dur- 
ing some  period  of  existence. 

Sub-phylum  1.  Adelochorda. 

Body  somewhat  worm-like  and  divided  into  pro- 
boscis,  collar,   and  trunk.     Notochordal  devel- 
opment slight. 
Class  Adelochorda. 

Characters  as  above.    (Dolichoglossus,  Balano- 
glossus.) 
Sub^phylum  2.  Urochorda. 

Adult  body  inclosed  in  a  tunic.     Larvae  usually 
motile.     Notochord  confined  to  the  tail  region. 
Class  Urochorda. 

Characters  as  above. 
Order  1.  Larvacea. 

Swim  throughout  life  by  means  of  a  tail.     The 
pharynx  has  a  single  pair  of  branchial   slits. 
(Appendicularia.) 
Order  2.  Thaliacea. 

Swim  by  forming  currents  of  water.    The  pharynx 
has  two  or  many  branchial  slits.  (Salpa,  Doliolum.) 
Order  3.  Ascidiacea. 

Mostly   fixed.     Pharynx    large,    provided    with 
many  branchial  slits.     (Molgula,  Perophora,  Bo- 
tryllus,  Amarcecium.) 
Sub-phylum  3.  Vertebrata. 

Notochord  or  vertebral  column  present  in  the 
adult  practically  throughout  the  length  of  the 
body.     Central  nervous  system  forms  a  dorsal 
nerve  tube. 
Division  1.  Acrania. 

Without  true  skull  or  highly  complex  brain. 
Class  1.  Acrania. 

Characters  as  above.     (Amphioxus.) 
Division  2.  Craniata. 

With  true  skull  and  highly  developed  brain. 
(Six  Classes  and  as  many  as  fifty-six  Orders  may  be  recog- 
nized under  this  Division.) 

174 


DOLICHOGLOSSTIS   (BALANOGLOSSUS)   KOWALEVSKII.        175 

Conklin:  Organization  and  Cell  Lineage  of  the  Ascidian  Egg.     Jour.  Acad. 

Nat.  Sci.,  Philadelphia,  2d  Ser.,  13.  1905. 
:  Does  Half  of  an  Ascidian  Egg  Give  Rise  to  a  Whole  Larva?    Arch. 

f.  Entwicklungsm.  d.  Org.,  21,  1906. 
Metcalf :  Notes  on  the  Morphology  of  the  Tunicata.     Zool.  Jahr.,  13, 1900. 


UROCHORDA. 
DOLICHOGLOSSUS   (BALANOGLOSSUS)   KOWALEVSKII. 

In  the  natural  habitat,  note  the  character  of  the  bottom 
where  Dolichoglossus  is  found:  Is  the  sand  clean  or  is  there  an 
admixture  of  organic  material?  Note  the  frail  tube  of  sand 
particles  fastened  together  with  mucus,  and  the  numerous 
"castings."  The  animal  has  a  characteristic  and  unpleasant 
odor. 

Note  the  division  of  the  body  into  three  general  regions:  (1) 
A  yellowish-white  „  conical  proboscis;  (2)  the  collar,  which  is 
brilliant  orange-red,  especially  in  males,  with  a  white  ring  pos- 
teriorly; and  (3)  the  trunk,  which  is  mainly  orange-yellow, 
shading  to  a  greenish-yellow  in  the  transparent  posterior  region, 
which  is  often  broken  off  when  the  animal  is  collected. 

The  trunk  may  be  roughly  divided  into  the  following  regions, 
which  overlap:  (a)  An  anterior  branchial  region,  bearing  on 
each  side  not  far  from  the  dorsal  median  line  a  row  of  transverse 
gill  slits;  (6)  a  genital  region,  bearing  on  each  side  of  the  body 
an  irregular  and  broken  fold  or  ridge  containing  the  reproductive 
organs,  which  are  gray  in  the  female  and  yellow  in  the  male; 
(c)  a  posterior  abdominal  region,  of  much  smaller  diameter  than 
the  rest  of  the  body. 

The  mouth  is  situated  on  the  ventral  side  at  the  base  of  the 
proboscis,  and  is  concealed  by  the  free  anterior  edge  of  the  collar. 
The  animal  is  unable  to  close  its  mouth,  and  in  burrowing  a 
continuous  stream  of  sand  passes  through  the  alimentary  canal, 
forming  the  "castings"  which  are  abundant  in  the  natural 
habitat  of  the  animal.  What  must  be  the  nature  of  its  food? 

Burrowing  is  effected  partly  by  muscular  contractions  of  the 
body-wall,  but  mainly  through  the  power  of  the  proboscis  and 


176  CHORDATA. 

collar  to  become  turgid.  In  burrowing  and  feeding,  of  what 
use  to  the  animal  is  the  collar? 

Note  the  characteristic  coiling  of  the  genital  region  in  this 
species.  The  anterior  end,  including  the  branchial  region,  is 
normally  maintained  in  a  vertical  position.  The  posterior 
end  is  also  kept  upright,  and  can  be  moved  up  and  down  in  a 
vertical  shaft  opening  on  the  surface,  thus  enabling  the  animal 
to  eject  the  residue  of  sand  from  the  anus. 

For  the  internal  anatomy,  the  account  in  the  Cambridge 
Natural  History  may  be  consulted.  Important  chordate 
characters  are  the  notochord,  the  dorsal  central  nervous  system, 
and  the  branchial  arches. 

Agassiz:  The  History  of  Balanoglossus  and  Tornaria.    Amer.  Acad.  Arts 

and  Sci.,  9,  1873. 
Hitter  and  Davis:  Studies  on  the  Ecology,  Morphology,  and  Speciology  of 

the  Young  of  Some  Enteropneusta  of  Western  North  America.    Univ. 

Calif.  Pub.  Zool,  1,  1904. 

MOLGULA  MANHATTENSIS. 

Specimens  of  this  simple  ascidian  may  be  found  attached  to 
old  piles,  associated  with  many  other  forms.  In  some  localities 
they  may  be  so  abundant  as  to  practically  incrust  the  piles,  and 
crowd  each  other  out  of  shape.  Examine  such  a  mass  and  see 
how  different  sized  individuals  are  associated.  Pull  them  apart 
and  see  if  there  is  any  tissue  connection  between  them  that 
would  indicate  a  definite  relation  between  neighbors.  Do  you 
understand  how  the  individuals  get  started  in  the  places  where 
they  are  attached  ?  With  a  glass-bottomed  pail  you  can  see  the 
expanded  individuals  on  the  piles,  but  they  can  be  more  satisfac- 
torily studied  in  small  dishes  of  sea-water. 

1.  Observe  the  contraction  and  closure  of  the  two  siphons 
when  the  animal  is  irritated. 

2.  Add  a  little  powdered  carmine  to  the  water  to  determine 
which  is  the  incurrent  or  oral  and  which  the  excurrent  or  atrial 
siphon. 

3.  Ascertain  the  number  of  lobes  at  the  extremity  of  each 
siphon.    Are  pigment-spots  present  on  the  siphonal  lobes? 


MOLGULA   MANHATTENSIS.  177 

Certain  organs  are  distinguishable  through  the  tough  tunic 
which  incloses  the  body.  The  endostyle  in  the  mid-ventral  line 
of  the  pharynx  or  branchial  basket  will  serve  as  a  guide  in  orient- 
ing the  animal.  Determine  dorsal,  ventral,  anterior,  right  and 
left  aspects. 

Make  a  drawing  of  an  expanded  animal. 

4.  The  tunic  or  test  can  be  removed  by  cutting  through  it 
with  scissors,  taking  care  not  to  injure  the  mantle  or  body-wall. 
Enlarge  the  opening  made  in  the  tunic  and  strip  it  from  the  body. 
Where  is  the  tunic  most  firmly  attached?    Examine  a  small 
piece  of  the  tunic  microscopically.    Are  blood-vessels  visible 
in  it?    Does  it  contain  any  cells? 

5.  For  further  study  use  both  fresh  and  preserved  material 
from  which  the  tunic  has  been  removed.     Identify  as  many 
organs  as  possible  through  the  mantle.     In  a  living  specimen 
note  the  beating  of  the  heart  (the  heart  is  on  the  right  side)  and 
the  frequent  reversal  of  the  direction  of  the  pulsations.    The 
endostyle,  longitudinal  pharyngeal  folds,  intestine,  gonads,  gono- 
ducts,  renal  organ,  and  subneural  gland  are  also  visible  through 
the  mantle. 

6.  Note  the  muscle  bands  of  the  mantle  which  serve  to  con- 
tract the  body  and  especially  the  siphons.     Where  are  the  mus- 
cles best  developed?    Is  there  any  definite  arrangement  of  the 
muscle-bands? 

7.  Fix  a  large  specimen  by  pins  through  the  siphons,  and 
with  scissors  and  fine  forceps  remove  a  large  section  of  the  man- 
tle from  the  left  side,  injuring  the  underlying  pharynx  as  little 
as  possible.    The  large  space  between  the  pharynx  and  the 
mantle,  laterally  and  dorsally,  is  the  atrium,  or  peribranchial 
chamber,  which  is  formed  as  an  ectodermal  involution.     Into 
this  atrial  cavity  open  the  intestine  and  the  gonoducts,  and  also 
the  numerous  stigmata  of  the  pharynx. 

Alimentary  Canal. — Cut  out  a  piece  of  the  wall  of  the  pharynx 
from  a  very  fresh  specimen  and  examine  in  sea-water  with  a 
microscope. 

1.  Note  the  meshwork  of  blood-vessels,  and  the  openings  or 
12 


178  CHOEDATA. 

stigmata,  lined  with  actively  moving  cilia.    Of  what  use  are  these 
cilia? 

2.  On  each  side  of  the  pharynx  six  longitudinal  pharyngecJ 
folds  will  be  seen.       -  • 

3.  The  endostyle  is  a  ciliated  groove  along  the  mid-ventral 
wall.     Anteriorly  it  is  continuous  with  the  peri-pharyngeal  cili- 
ated bands,  which  encircle  the  oral  end  of  the  pharynx.     From 
the  point  where  they  unite  dorsally  the  dorsal  lamina  extends 
backward  along  the  mid-dorsal  line  of  the  pharynx.     At  its 
posterior  end  will  be  seen  the  small  opening  into  the  esophagus. 

Do  you  understand  how  the  animal  captures  its  food  and 
how  the  endostyle,  peri-pharyngeal  bands,  and  dorsal  lamina  are 
used? 

4.  In  front  of  the  anterior  end  of  the  dorsal  lamina  note  the 
small,  volute-shaped  dorsal  tubercle.    This  is  the  extremity  of 
the  hypophysis,  a  tube  connecting  the  subneural  gland  with  the 
oral  cavity. 

5.  A  ring  of  oral  tentacles  will  be  seen  in  the  mouth,  anterior 
to  the  peri-pharyngeal  bands.     Of  what  use  are  tentacles  in 
the  mouth?    How  many  tentacles  are  there? 

6.  The  very  short  esophagus  opens  into  the  stomach,  which 
will  be  recognized  by  the  brown  digestive  glands  that  cover 
it.     From  the  stomach  the  intestine  forms  a  loop  on  the  left 
side,  and  is  easily  traced  to  the  anus,  which  opens  dorsal  to  the 
pharynx  in  the  atrial  chamber.    A  longitudinal  fold,  the  typh- 
losole,  extends  throughout  the  intestine.     What  is  the  use  of 
such  a  fold? 

Reproductive  System. — On  each  side  of  the  body,  adherent  to 
the  inside  of  the  mantle,  is  an  elongate  hermaphrodite  gland. 
Each  gland  consists  of  a  lighter  part,  the  testis,  and  a  darker  part, 
the  ovary.  The  gonoducts  open  on  the  outer  wall  of  the  atrial 
cavity  near  the  base  of  the  atrial  siphon.  Each  consists  of  two 
ducts,  oviduct  and  vas  deferens.  Microscopic  examination  of 
the  oviduct  may  show  the  presence  of  eggs. 

Excretory  System. — The  renal  organ  is  a  conspicuous,  elon- 
gated sac  on  the  right  side.  It  contains  a  brownish  fluid  and 
usually  some  solid  matter.  It  does  not  possess  a  duct. 


MOLGULA   MANHATTENSIS.  179 

Nervous  System. — The  cerebral  ganglion,  which  in  Molgula  is 
almost  completely  surrounded  by  the  subneural  gland,  lies  close 
to  the  mantle,  between  the  two  siphons,  and  is  thus  dorsal  to 
the  mouth.  Nerves  can  be  seen  passing  from  the  ganglion  to 
the  two  siphons.  The  hypophysis,  a  tube  leading  from  the  sub- 
neural  gland,  opens  as  the  dorsal  tubercle  above  mentioned. 

Circulatory  System. — 1.  The  heart,  which  lies  on  the  right 
side  between  the  hermaphrodite  gland  and  the  renal  organ,  is 
inclosed  within  a  pericardium  which  is  a  portion  of  the  crelom. 
It  should  be  studied  in  a  living  specimen,  with  the  aid  of  a  hand- 
lens. 

2.  If  a  very  small  Molgula  (one-eighth  of  an  inch  in  length) 
is  studied  alive  in  a  watch-glass  with  the  microscope,  the  course 
of  the  circulation,  and  the  frequent  reversal  of  its  direction,  can 
be  observed. 

3.  From  the  dorsal  end  of  the  heart  a  cardio-visceral  vessel 
runs  to  the  visceral  mass,  where  it  divides  into  smaller  vessels. 
These,  reuniting,  form  the  viscero-branchial  vessel  which  extends 
along  the  dorsal  surface  of  the  pharynx  above  the  dorsal  lamina. 
Numerous  small  branchial  vessels  in  the  pharyngeal  wall  connect 
this  vessel  with  the  branchio-cardiac,  which  lies  ventral  to  the 
endostyle  and  unites  with  the  ventral  end  of  the  heart.    The 
frequent  reversal  of  the  current  can  be  readily  seen  both  in  the 
heart  and  in  the  vessels. 

The  relation  of  the  parts  will  be  more  clearly  understood  if 
a  second  large  specimen  is  dissected  as  follows:  With  scissors 
cut  off  the  atrial  siphon,  thus  exposing  the  atrium;  then  simi- 
larly remove  by  a  single  cut  the  oral  siphon,  together  with  the 
anterior  end  of  the  pharynx  (the  piece  thus  cut  off  should  contain 
the  ganglion,  dorsal  tubercle,  peri-pharyngeal  bands,  oral  tentacles, 
anterior  portion  of  the  endostyle,  dorsal  lamina,  etc.). 

Make  drawings  that  will  show  the  structure. 

Hunter:  Notes  on  the  Heart  Action  of  Molgula  manhattensis.     Am.  Jour. 

Physiol.,  10,  1903. 
Kingsley:  Some  Points  in  the  Development  of  Molgula.    Proc.  Bost.  Soc. 

Nat.  Hist.,  21,  1883. 


180  CHOEDATA. 


PEROPHORA. 

This  colonial  simple  ascidian  occurs  on  piles  and  other  sub- 
merged materials,  and  is  commonly  attached  by  branching 
stolons  to  seaweeds,  simple  tunicates,  or  other  sessile  animals. 
Material  should  be  quite  fresh  for  satisfactory  study,  and  should 
be  carefully  handled  to  avoid  crushing.  Study  in  a  watch-glass 
of  sea-water  (or  support  the  cover-glass),  with  a  low  power  of  the 
microscope. 

1.  Notice  that  the  individuals  are  essentially  very  much  like 
miniature  Molgulas.     Identify  as  many  of  the  organs  that  were 
seen  in  Molgula  as  possible,  noting  the  differences. 

2.  The  form  illustrates  the  type  (Clavelinidse)  in  which  a 
colony  is  formed  by  budding  from  a  stolon,  but  in  which  the 
individuals  retain  their  identity  to  a  great  degree  and  have  sepa- 
rate tunics. 

3.  Study  the  stolon  with  its  flattened  epicardiac  tube.    This 
tube  is  derived  from  the  branchial  sac  and  is  accordingly  endo- 
dermic. 

4.  Study  buds  of  various  sizes  and  see  how  the  inner  vesicles 
arise  from  the  epicardiac  tube. 

5.  Try  to  make  out  the  entire  course  of  the  circulation  of  the 
blood.     Notice  especially  the  heart,  branchial  vessels,  vessels  of 
the  mantle,  and  the  circulation  of  the  stolon.     Watch  the  pulsa- 
tions of  the  heart  and  see  the  reversal  of  the  blood-current.     Is 
the  heart-beat  synchronous  in  different  individuals?    What  part 
of  the  blood  is  colored  ? 

6.  Study  the  action  of  the  cilia  in  the  gill  clefts. 
Drawings  of  a  colony  and  of  an  individual  are  desirable. 

Lefevre:  Budding  in  Perophora.    Jour.  Morph.,  14,  1898. 


BOTRYLLUS. 

The  small,  radially  arranged  colonies  of  this  composite  ascidian 
are  common  on  eel-grass,  from  which  they  may  be  separated  by 
means  of  a  knife,  and  studied  alive  in  a  watch-glass  with  a  low 


AMARGECIUM.  181 

power  of  the  microscope.    The  cleaner  and  more  transparent 
colonies  should  be  selected. 

1.  Note  the  character  which  makes  the  form  a  "composite" 
ascidian — the  common  tunic  or  test.    Find  the  mouths  and  the 
common  cloacal  cavity.    Would  it  be  correct  to  say  that  a  common 
atrium  is  present  ? 

2.  Find  the  annular  blood-vessel  and  its  numerous  ampullce. 
Do  you  observe  any  striking  facts  regarding  the  circulation? 
What  function  have  the  ampullae? 

3.  With  your  knowledge  of  Molgula  as  a  guide,  identify  as 
many  of  the  organs  as  possible.     (This  is  sometimes  difficult 
because  of  pigment.) 

4.  Very  young  colonies,  with  only  the  first  one  or  two  genera- 
tions of  buds,  may  also  be  found  on  eel-grass,  appearing  as  trans- 
parent hemispherical  lumps  about  a  millimeter  in  diameter. 
These  should  be  fixed  and  stained  on  the  eel-grass,  and  later 
mounted  (either  still  attached  or  removed)  in  balsam.    These 
will  show  very  clearly  the  formation  of  buds  of  the  "parietal" 
or  "peribranchiar  type.     (In  this  type  the  outer  vesicle  arises 
from  the  integument,  and  the  inner  vesicle  from  the  parietal 
wall  of  the  atrial  cavity.)     The  inner  vesicle  may  be  seen  partly 
constricted  into  three  divisions — the  pharynx  and  the  two  atrial 
sacs.    From  which  "germ  layer"  then  are  these  parts  in  the 
bud  derived  ? 

5.  Look  for  the  tailed  larvae  or  "tadpoles"  near  the  surface 
and  on  the  side  turned  toward  the  light,  in  a  dish  in  which  Bot- 
ryllus  has  been  kept  for  an  hour  or  two.     Is  this  positive  photo- 
trophism  advantageous?    Examine  a  larva  under  a  microscope. 

Drawings  of  the  adult,  the  young  colony,  and  the  larva  are  de- 
sirable. 

AMAROECIUM.    (Sea-Pork.) 

Different  species  of  this  composite  ascidian  live  at  different 
depths  and  show  minor  structural  differences,  especially  in  the 
tests.  Colonies  may  be  found  abundantly  on  piles  and  they  are 
frequently  brought  up  with  a  dredge. 


182  CHOBDATA. 

1.  Compare  the  grouping  of  the  individuals  in  the  colony 
with  Botryllus.     Is  there  any  regularity  in  the  number  of  a 
group  connected  with  a  common  cloacal  cavity? 

2.  With  a  sharp  knife,  cut  a  section  vertical  to  the  surface  of 
the  mass,  and  two  or  three  millimeters  thick,  and  study  it  with 
a  low  power  of  the  microscope.     Other  pieces  should  be  squeezed 
in  a  finger-bowl  half  full  of  sea-water,  the  expressed  material 
(adult   animals,   fragments,  embryos,  etc.)   allowed  to  settle, 
and  then  rinsed  with  clean  sea-water.    A  few  entire  adults  may 
be  picked  out  with  a  pipet. 

In  the  adult  animal  you  may  find: 

(a)  Oral  and  atrial  openings. 

(b)  Pharynx,  with  the  peri-pharyngeal  bands  and  endostyle, 
esophagus,  the  orange-brown  corrugated  stomach,  and  intestine. 

(c)  The  cerebral  ganglia. 

(d)  The  long  post-abdomen,  with  its  hollow  epicardium  con- 
nected with  the  pharynx.     (The  post-abdomen  is  really  a  stolon. 
Recall  Perophora.)     If  complete,  the  red-pigmented  tip  will  be 
seen. 

(e)  The  slowly  pulsating  U-shaped  heart,  situated  very  near 
the  tip  of  the  post-abdomen. 

3.  In  the  atrium,  which  serves  as  a  brood-pouch,  embryos 
in  all  stages  may  be  found.     How  do  the  eggs  compare  in  size 
with  those  of  Molgula? 

4.  Look  for  buds  formed  by  segmentation  of  the  post-abdo- 
men (stolon).    The  "inner  vesicle "  of  these  buds,  which  gives 
rise  to  the  alimentary  canal  and  atrial  sacs,  comes  from  the 
endodermic  epicardium,  as  in  Perophora.     Compare  this  with 
Botryllus. 

5.  If  the  material  squeezed  in  the  finger-bowl  was  quite  fresh, 
living  embryos  in  all  stages  of  development  can  be  found,  and 
the  tailed  larvse  will  probably  be  found  hatching  during  the  first 
hour  or  two.     These  swim  rapidly,  and  usually  swim  away  from 
the  light.    Does  this  correspond  with  Botryllus?    Is  this  nega- 
tive phototrophism  adaptive? 


SALPA   CORDIFORMIS.  183 

The  tailed  larvae  may  be  picked  up  with  a  pipet  while  swim- 
ming (the  dead  ones  on  the  bottom  of  the  dish  should  not  be 
used),  dropped  into  fixing  fluid,  and  finally  stained  and  mounted 
in  balsam.  Some  larvae  will  be  found  attached  to  the  dish  by 
their  adhesive  organs.  Notice  where  these  organs  are  sit- 
uated. 

In  larvae  that  have  been  previously  stained  and  mounted 
observe: 

(a)  The  shape  of  the  animal  and  its  division  into  body  and 
tail. 

(6)  The  thick  test,  and  the  oral  and  atrial  openings. 

(c)  The  adhesive  organs.     How  many  are  there? 

(d)  The  notochord.    How  far  does  it  extend?    • 

(e)  The  tail  muscles. 

(/)  The  pharynx,  with  as  yet  few  gill  clefts,  the  endostyk, 
esophagus,  stomach,  intestine,  and  yolk-mass. 

(g)  The  cerebral  vesicle  with  the  eye-spot  and  otolith. 

If  young  individuals  that  have  been  attached  but  a  short 
time,  but  have  lost  their  tails,  are  stained  and  mounted,  they 
will  be  found  very  instructive  when  compared  with  the  larva. 
The  complete  degeneration  of  the  tail  and  the  final  rotation 
into  the  position  of  the  adult  can  be  traced  in  a  series  of  indi- 
viduals. 

Drawings  of  an  adult  individual,  of  a  larva,  and  of  a  young 
individual  are  desirable. 

Van  Name:  Compound  Ascidians  of  the  Coasts  of  New  England  and  Neigh- 
boring Provinces.     Proc.  Bost.  Soc.  Nat.  Hist.,  34,  1910. 

SALPA  CORDIFORMIS. 

Examine  a  specimen  in  a  bowl  of  water  without  dissecting. 
Use  a  hand-lens. 

Sexual  form  (occurring  in  chains) : 

1.  Note  the  transverse  muscle  bands.  How  many  bands  are 
there?  Are  they  complete  or  interrupted?  Do  you  know  what 
they  are  for? 


184  CHOBDATA. 

2.  The  oral  aperture  is  dorsal  and  far  forward.    Are  there 
any  muscles  for  opening  and  closing  it? 

3.  What  is  the  form  and  position  of  the  cloacal  aperture? 
Is  it  provided  with  muscles? 

4.  Observe  the  processes  of  the  tunic,  one  anterior,  one  mid- 
ventral,  and  two  posterior.    These  processes  (except  the  dorsal 
posterior)  serve  to  unite  the  individuals  of  the  chain. 

5.  Does  the  animal  show  perfect  bilateral  symmetry? 

6.  Posterior  to  the  mouth,  the  ganglion  and  the  pigmented 
eye-spot  may  be  found.      Immediately  anterior  to  these  is  the 
elongate  hypophysis. 

7.  Note  the  endostyle  in  the  floor  of  the  pharynx,  and  the 
dorsal  lamina  between  the  pharynx  and  atrial  cavity.     From  the 
anterior  end  of   the   dorsal   lamina   the  peri-pharyngeal  bands 
extend  to  the  anterior  end  of  the  endostyle. 

8.  The  pharynx  communicates  laterally  with  the  atrium  by 
means  of  two  very  large  stigmata.     These  are  probably,  homol- 
ogous with  the  numerous  stigmata  of  Molgula.  - 

9.  The  "nucleus,"  the  large  mass  in  the  posterior  end  of  the 
body,  contains  the  stomach  and  intestine. 

The  ova  are  fertilized  by  spermatozoa  from  individuals  of 
another  chain,  since  in  the  same  chain  the  spermatozoa 
mature  much  later  than  the  ova.  The  fertilized  ova  migrate  to 
a  spot  in  the  right  wall  of  the  atrium,  where  they  develop  into 
the  solitary  non-sexual  Salpa. 

In  this  species  as  many  as  three  or  four  embryos  may  be  seen 
attached  by  "placentce"  to  the  cloacal  wall  on  the  right  side. 
The  placental  connection  finally  separates,  and  the  embryo 
passes  out  through  the  cloacal  aperture. 

Make  an  enlarged  drawing  (a  latero-dorsal  view  is  best). 

Brooks:  The  Genus  Salpa.     Mem.  Biol.  Lab.  Johns  Hopkins  Univ.,  2, 1893. 
Grobben:  Doliolum  und  sein  Generationwecksel.     Arb.  Zool.  Inst.  Wien.,  4, 
1882. 


AMPHIOXUS   LANCEOLATUS.  185 


ACRANIA. 

AMPHIOXUS  LANCEOLATUS. 

While  living  material  is  not  easily  provided  for  laboratory 
work,  it  should  be  understood  that  this  form  spends  most  of  its 
time  in  the  sand  of  the  bottom,  in  which  it  burrows  with  great 
ease  by  movements  of  the  body. 

1.  In  an  alcoholic  specimen  note  the  dorsal,  ventral,  and 
caudal  regions  of  the  median  fin,  metapleural  folds,  muscle  plates 
or  myotomeSj  buccal  cavity  fringed  with  cirri,  atriopore,  and  anus. 

2.  Using  a  specimen  that  has  been  macerated  in  20  percent 
nitric  acid,  remove  the  skin  and  myotomes  from  the  right  side 
very  carefully,  by  means  of  needles,  exposing  the  notochord,  nerve 
cord,  gonads,  and  the  entire  alimentary  canal  (pharynx,  intestine, 
and  digestive  diverticulum  or  "liver,"  which  lies  along  the  right 
side  of  the  pharynx). 

3.  Examine  microscopically  and  notice: 

(a)  The  nerve  cord,  cerebral  vesicle,  cerebral  nerves,  eye-spot, 
and  pigment  cells.    Note  also  the  alternate  metamerism  of  the 
spinal  nerves. 

(b)  The  buccal  skeleton. 

(c)  A  large  piece  of  the  pharyngeal  wall. 

4.  Examine  an  Amphionus  one  centimeter  in  length,  stained 
and  mounted. 

Identify  as  many  as  possible  of  the  structures  mentioned 
above,  and  in  addition  note:  the  olfactory  pit,  oral  velum  with 
velar  tentacles,  and  u  taste  organ"  in  the  buccal  cavity. 

A  drawing  showing  the  general  structure  is  desirable. 

5.  Make  thick   free-hand   sections  of   various  regions   and 
study  with  a  low  power  in  a  watch-glass,  to  supplement  the  study 
of  stained  sections. 

6.  Prepared  sections  should  be  studied  that  show  the  follow- 
ing five  regions:  (a)  buccal  cavity;   (b)  anterior  part  of  pharynx; 
(c)  posterior  part  of  pharynx  with  gonads  and  liver;    (d)  atrio- 
pore; (e)  anus. 


186  CHOBDATA. 

The  five  sections  should  be  studied  with  a  low  power  and 
drawn.  In  (b)  (anterior  part  of  pharynx),  note  especially  the 
limits  of  the  ccelom  and  atrium,  the  lymph-spaces  in  the  meta- 
pleural  folds,  the  two  dorsal  aortce,  the  ventral  aorta,  the  epibran- 
chial  groove,  the  endostyle,  the  sub-endostylar  ccelom,  and  the  two 
kinds  of  gill-bars,  primary  and  tongue-bars. 

With  a  high  power  study  the  nerve  cord  (best  shown  in  re- 
gion a)  and  the  gill-bars  and  endostyle  (best  shown  in  region  6). 

Drawings  of  these  regions  are  desirable. 

Willey:  Amphioxus  and  the  Ancestry  of  Vertebrates.    Columbia  Univ. 
Press. 


NOTES  FOR  GUIDANCE  IN  MAKING  PERMANENT 
PREPARATIONS. 

Only  very  simple  directions  are  here  given,  such  as  will 
serve  to  aid  students  who  have  had  no  experience  in  preparing 
objects  for  microscopic  examination  to  make  preparations  when 
this  is  desirable  for  proper  laboratory  study.  Those  who  desire 
to  prepare  material  for  serial  sections,  or  who  wish  to  make 
whole  mounts  of  delicate  material,  are  referred  to  Lee's  Micro 
tomist's  Vade  Mecum.  Short  directions  for  preparing  forms 
like  Paramsecium  are  given  on  p.  191. 

The  steps  taken  in  preparing  total  mounts  include: 

1.  Fixing,  or  killing. 

2.  Washing. 

3.  Dehydrating  and  staining. 

4.  Clearing. 

5.  Mounting. 

Fixing. — This  is  necessary  to  keep  the  cells  and  tissues  as 
nearly  as  possible  in  their  natural  position,  shape,  and  structure, 
and  in  order  that  the  protoplasm  composing  them  may  be  kept 
in  condition  to  stain  satisfactorily. 

In  selecting  a  fixing  agent  remember: 

1.  If  the  material  is  highly  irritable  and  contractile,  it  will 
have  to  be  killed  practically  instantly  with  hot  solutions,  or 
be  previously  narcotized. 

2.  If  there  is  much  lime,  an  agent  that  contains  much  acid 
should  not  be  used,  as  the  lime  will  be  dissolved  and  the  bubbles 
of  gas  are  likely  to  tear  or  distort  tissues. 

3.  Where  rapid  fixation  is  desirable,  as  in  expanded  hydroids 
and  the  like,  sublimate-acetic  (hot)  is  preferable.     Where  the 
tissue,  or  the  animal,  is  not  specially  muscular,  or  liable  to  contrac- 
tion, any  of  the  fluids  can  be  used.    The  time  objects  should 
be  left  in  the  killing  solution  varies,  approximately,  directly  as 

187 


188        GUIDANCE  IN  MAKING   PERMANENT   PREPARATIONS. 

their  size.  Three  minutes  will  suffice  for  killing  hydroids  in 
sublimate-acetic. 

Washing. — All  objects  must  be  thoroughly  washed,  after  using 
most  killing  agents.  This  may  be  done  with  repeated  changes 
of  fresh  water  or  with  alcohol,  beginning  with  a  low  grade  and 
gradually  working  up  to  70  percent.  With  most  small  objects 
alcohol  is  preferable,  but  if  the  object  is  large  this  is  too  expen- 
sive. 

In  case  a  fixing  agent  is  used  which  is  an  alcoholic  solution, 
wash  out  in  the  same  grade  of  alcohol  used  in  making  the  fixing 
agent. 

Dehydrating  and  Staining. — From  water,  all  objects  should 
be  placed  successively  in  35  percent,  50  percent,  and  70  percent 
alcohol,  five  to  fifteen  minutes  in  each  for  small  objects.  In 
subsequent  changes  from  one  grade  to  another  allow  about  the 
same  time.  All  tissues  killed  in  a  corrosive  sublimate  mix- 
ture should  now  be  treated  with  a  weak  solution  of  iodin,  to 
dissolve  the  corrosive  sublimate  that  still  remains,  and  thus 
prevent  the  later  formation  of  crystals  of  that  substance. 
Such  crystals  would  not  appear  immediately,  but  ever  increas- 
ingly, as  the  preparation  is  kept.  Put  a  few  drops  of  iodin 
into  the  70  percent  alcohol  containing  the^object,  leave  a  few 
minutes,  and,  if  the  yellow  color  caused  by  the  iodin  has  disap- 
peared, turn  off  the  alcohol  and  use  more  70  percent  alcohol 
with  iodin,  as  before.  The  bleaching  indicates  that  some  cor- 
rosive sublimate  remains.  Repeat  until  the  yellow  color  does 
not  fade.  Then  wash  in  clear  70  percent  alcohol.  At  this  point 
either  staining,  or  preparation  for  so  doing,  begins. 

In  case  the  stain  you  wish  to  use  is  a  70  percent  alcoholic 
solution,  it  may  be  used  immediately.  Otherwise,  the  object 
must  be  run  through  the  grades  of  alcohol,  up  or  down  as  the 
case  may  be,  to  that  medium  in  which  the  stain  to  be  used  is 
dissolved.  If  an  aqueous  stain  such  as  alum-carmine  is  to  be 
used,  pass  through  50  percent  and  35  percent  alcohol  to  water. 
If  a  95  percent  alcoholic  stain  is  to  be  used,  pass  through  80  per- 
cent and  95  percent  alcohol. 


CLEARING  AND  MOUNTING.  189 

The  time  an  object  should  be  treated  with  stain  varies  with 
the  stain  and  the  size  of  the  object.  Alum-carmine  should  be 
used  from  six  to  twenty  hours,  according  to  circumstances. 
Borax-carmine  should  be  used  from  five  minutes  to  half  an  hour. 
Aceto-carmine,  used  for  killing  and  staining,  acts  very  rapidly. 
Delafield's  hematoxylin  (a  dark  wine-colored  solution  in  water) 
requires  ten  minutes  to  half  an  hour.  In  all  these  cases,  exam- 
ination of  the  objects  themselves  is  the  only  means  of  deciding 
when  staining  is  sufficient.  It  is  usually  best  to  slightly  over- 
stain  and  then  to  bleach  out,  as  certain  parts  of  the  protoplas- 
mic structure  will  retain  the  stain  better  than  others  and  thus 
better  differentiation  will  be  secured.  After  staining,  bring 
the  tissues  gradually  into  70  percent  alcohol,  and  then  treat 
with  acidulated  alcohol  to  remove  excess  of  stain.  After  this, 
every  trace  of  the  acid  must  be  removed  by  washing  in  clean 
alcohol,  or  the  tissues  will  continue  to  bleach  after  they  are 
mounted.  The  specimen  is  now  ready  for  final  dehydration. 
In  damp  climates,  as  at  the  seashore,  your  stronger  alcohols 
must  be  kept  closely  covered  all  of  the  time  or  they  will  take 
water  from  the  atmosphere  and  be  unfit  for  the  purpose.  Run 
through  80  percent,  95  percent,  and  100  percent  alcohol,  thus 
completing  dehydration.  Every  trace  of  water  must  be  removed 
and  then  kept  out. 

Clearing  and  Mounting. — From  absolute  alcohol,  place  objects 
in  some  clearing  fluid  (clove  oil,  cedar  oil,  or  xylol)  and  leave 
till  they  have  a  clear,  translucent  appearance,  after  which  place 
on  a  clean  slide,  with  come  Canada  balsam  or  dammar,  and  cover 
with  a  cover-glass. 

If  the  object  turns  cloudy  or  milky  when  placed  in  the  clean- 
ing fluid,  it  is  evidence  that  all  of  the  water  has  not  been  removed, 
and  it  should  be  returned  to  absolute  alcohol  for  complete  dehy- 
dration. Tissues  left  in  the  clove  oil  or  xylol  for  any  great 
length  of  time  will  become  hard  and  brittle.  In  case  tissues 
in  the  process  of  preparation  must  necessarily  be  left  untreated 
for  several  days,  they  should  be  left  in  a  70  percent  or  80  percent 
alcoholic  medium. 


190       GUIDANCE   IN   MAKING   PERMANENT  PREPARATIONS. 

Sectioned  Material. — In  a  few  cases  sectioned  material  may 
be  distributed  to  the  class.  Be  sure  that  the  slide  on  which  you 
intend  mounting  the  sections  is  thoroughly  clean.  Remove  any 
greasy  substance  with  95  percent  alcohol.  On  a  cleaned  slide, 
smear  a  very  little  albumen  fixative  with  your  finger-tip  and  re- 
move all  except  the  thinnest  film.  Now  place  the  sections  on  the 
albumen  over  an  area  the  size  of  the  cover-glass  to  be  used,  and 
press  them  down  flat  with  the  tip  of  a  clean,  dry  finger.1  Warm 
the  slide  over  an  alcohol  lamp  very  carefully  until  the  paraffin 
in  which  the  sections  are  embedded  is  just  melted.  While  the 
paraffin  is  still  melted  treat  it  with  xylol  (a  jar  containing  xylol 
for  this  purpose  is  desirable).  This  will  dissolve  the  paraffin  and 
leave  the  sections  alone  adhering  to  the  slide.  When  the  paraf- 
fin is  completely  dissolved  (this  will  take  but  a  few  seconds), 
drain  off  the  xylol,  apply  a  drop  of  balsam,  and  cover  as  in  total 
mounts.  The  preparation  is  now  ready  for  use,  and  is  per- 
manent, but  must  be  handled  carefully  while  fresh. 

Application  of  above  directions  in  the  case  of  a  hydroid : 
Hot  corrosive,  fifteen  seconds. 
Cold  corrosive,  five  minutes. 
Water  or  alcohol,  four  changes,  three  or  four  minutes 

each. 
Thirty-five  percent,  50  percent,  and  70  percent  alcohol, 

five  minutes  each. 
Seventy  percent  alcohol  plus  iodin,  as  in  directions  above. 

One-half  of  your  material  may  now  be  placed  in  borax-carmine. 
Leave  the  material  in  this  till  objects  have  taken  on  a  good  color. 
(Ask  an  instructor  about  this.)  When  sufficiently  stained,  put 
into  acidulated  alcohol  till  the  color  assumes  a  brilliant  appear- 
ance, but  do  not  allow  it  to  fade  too  far.  Wash  in  70  percent  and 

1If  the  sections  are  not  needed  for  study  for  a  day  or  more,  they  may 
be  floated  out  on  water  placed  over  the  film  of  albumen.  Heat  the  water 
until  the  sections  stretch  out  flat,  but  do  not  melt  the  paraffin.  In  not 
less  than  twelve  hours  after  the  slide  is  thoroughly  dry,  it  may  be  treated 
as  directed  in  the  other  case.  The  value  of  this  method  is  that  it  gives 
perfectly  flat  sections. 


PROTOZOA  METHODS.  191 

then  run  through  80  percent,  95  percent,  and  100  percent  alcohol, 
five  minutes  in  each,  thence  into  clove  oil,  or  cedar  oil,  keeping  all 
reagents  carefully  covered,  and  leave  till  the  object  is  thoroughly 
penetrated.  This  latter  process  may  take  five  to  ten  minutes. 

If,  on  putting  your  objects  into  the  clearing  medium,  the 
latter  exhibits  a  milky-white  appearance,  the  material  is  not 
sufficiently  dehydrated,  and  must  be  returned  to  100  percent 
alcohol. 

After  clearing  is  completed,  put  the  object  on  a  clean  slide 
with  a  little  balsam  and  cover. 

The  material  not  treated  with  borax-carmine  may  be  run 
back  through  50  percent  and  35  percent  alcohols  to  water,  to 
which  a  few  drops  of  hematoxylin  have  been  added,  or  put  from 
water  into  alum-carmine.  The  former  stain,  if  dense,  should  not 
require  over  twenty  to  thirty  minutes,  but  objects  must  be  left 
in  alum-carmine  ten  to  twenty  hours.  When  a  good  color  is 
obtained,  run  the  material  through  the  grades  of  alcohol,  from  the 
lowest  to  the  highest  (five  minutes  in  each),  and  mount  as  in  the 
case  of  the  borax-carmine  objects. 

Objects  stained  in  alum-carmine  will  probably  not  overstain; 
but  excess  of  hematoxylin  should  be  extracted  with  acidulated 
alcohol  when  the  70  percent  grade  is  reached,  after  which  it  is 
very  essential  that  all  of  the  acid  be  removed  by  repeated  changes 
of  70  percent  alcohol.  Otherwise  the  objects  will  fade. 

Protozoa  Methods. — A  simple  method  for  preparing  such 
forms  as  Paramsecium  is  as  follows: 

Kill  in  Sublimate  Acetic  (a  small  watch-glass  or  concave  slide 
is  a  good  container),  let  settle,  run  to  70  percent  alcohol,  drop 
on  a  slide  smeared  with  albumen  fixative,  let  it  remain  a  minute, 
then  thrust  the  slide  into  70  percent  alcohol.  Stain,  after 
running  to  grade  of  alcohol  or  water  in  which  stain  is  made 
(hsematoxylin  or  picro-cannine  is  good),  dehydrate,  clear,  and 
mount  as  usual. 


GLOSSARY. 


Abdomen.    The  posterior  division  of  the  body  of  an  arthropod. 

Aboral.     The  surface  away  from  the  mouth. 

Aciculum.     A  supporting  rod  in  a  parapodium  of  an  annelid. 

Acinous.     Saccular  or  granular. 

Acontium.     One  of  the  filaments  that  are  attached  to  the  mesenteries 

of  such  forms  as  Metridium. 

Adductor  muscle.     A  closing  or  withdrawing  muscle. 
Adhesive  organ.     A  sucker  or  sticky  pad  that  will  adhere. 
Ad-radial  canal.    A  canal  in  a  medusa  that  lies  between  adjacent  per- 

and  inter-radial  canals. 

Afferent.     Coming  toward,  as  a  vessel  that  leads  to  an  organ. 
Alga.     A  simple  plant. 
Alimentary  canal.     Digestive  tube. 

Alternation  of  generation.    Alternation  of  sexual  and  asexual  genera- 
tions in  the  life  cycle  of  an  organism. 
Alveolus.     A  little  sac  or  cavity;    also  one  of  the  plates  that  bears  the 

teeth  in  an  echinoid. 

Ambulacral  area.     The  region  bearing  the  tube  feet  of  an  echinoderm. 
Ambulacral  foot.     A  tube  foot  of  an  echinoderm. 
Ambulacral  groove.     One  of  the  depressions  in  which  the  tube  feet  of 

a  starfish  are  placed. 

Ambulacral  plate.     One  of  the  plates  of  an  ambulacral  area. 
Ambulacral  pore.     The  opening  through  which  a  tube  foot  projects. 
Ambulacral  ridge.    The  elevation  in  the  ccElom  of  a  starfish  arm,  caused 

by  the  ambulacral  plates. 

Ambulacral  sucker.    The  sucker  at  the  end  of  a  tube  foot. 
Amphiblastula.     An  embryonic  stage  of  a  sponge. 
Ampulla.     A  reservoir  connected  with  the  tube  foot  of  an  echinoderm. 
Anal  plate.     One  of  the  plates  in  the  periproct  of  an  echinoid. 
Analogous.     Similar  in  function. 

Anastomosis.    The  joining  together,  as  of  vessels  and  nerves. 
Antenna.    A  sensory  head  appendage  of  an  arthropod. 
Antennule.     A  sensory  head  appendage  of  an  arthropod,  placed  just 

anterior  to  the  antenna  when  present. 
13  193 


194  GLOSSAKY. 

Anterior.    Front  or  head  end. 

Antero-posterior.    Lengthwise  of  the  body. 

Anus.     The  posterior  opening  of  the  alimentary  canal. 

Aorta.     In  invertebrates  used  to  designate  the  chief  blood-vessel. 

Apical  system.     A  group  of  plates  surrounding  the  periproct  of  an 

echinoid. 
Apopyle.    The  opening  of  a  radial  canal  of  a  sponge  into  the  gastreal 

cavity  or  cloaca. 
Arthrobranch.    A  gill  of  a  crustacean  borne  by  the  articular  membrane 

at  the  base  of  an  appendage. 
Asexual.    Reproduction  by  other  than  sexual  methods,  as  by  budding 

or  division. 

Atriopore.    External  opening  of  the  atrium  of  Amphioxus. 
Auricle.    A  division  of  the  heart. 
Avicularium.    A  structure  shaped  like  a  bird's  head,  to  be  found  on 

some  of  the  Polyzoa. 
Axial  organ.    A  structure  near  the  stone  canal  of  echinodenns  that  is 

apparently  connected  with  the  genital  organs. 

Basipod.    Second  segment  from  the  body  of  a  crustacean  limb. 

Beak.  Horny  mouth  parts;  the  point  from  which  growth  has  proceeded 
in  a  clam  shell. 

Bilateral  symmetry.    Right  and  left  sides  alike. 

Biramous.    Composed  of  two  branches,  as  a  typical  crustacean  appendage. 

Bivalve.     Having  two  valves  or  pieces,  as  a  clam  shell. 

Bivium.  The  two  rays  of  a  starfish  that  are  nearest  the  madreporic 
plate. 

Blastostyle.    The  axial  tissue  of  a  reproductive  polyp  of  certain  Hydrozoa. 

Body-cavity.  Ccelom;  the  cavity  between  the  alimentary  canal  and  body- 
wall. 

Body-wall.    The  outer  wall  of  the  body. 

Brain.     In  invertebrates  frequently  applied  to  the  cerebral  ganglia. 

Branchiae.     Gills;  organs  adapted  for  aquatic  respiration. 

Branchial  heart.  An  accessory  heart  placed  at  the  base  of  the  gill,  as  in 
the  squid. 

Brood  sac.    A  cavity  or  pouch  in  which  developing  embryos  are  carried. 

Bud.    An  outgrowth  of  an  animal  that  will  become  a  new  individual. 

Byssal  thread.  One  of  the  threads  by  which  certain  lamellibranchs  attach 
themselves. 

Caecum.    A  sac-like  appendage  of  the  alimentary  canal. 
Calciferous  glands.    Esophageal  glands  of  some  annelids. 
Carapace.    Head  and  thoracic  covering  of  some  crustaceans. 


GLOSSAEY.  195 

Cardiac  division  of  stomach.    Anterior  or  first  division. 
Carpopod.     Fifth  segment  from  the  body  of  the  leg  of  a  crustacean. 
Cellulose.    The  material  that  forms  the  walls  of  plant  cells. 
Cephalont.     Attached  stage  in  the  life-history  of  Gregarina. 
Cephalothorax.     Fused  head  and  thorax  of  many  crustaceans. 
Cervical  groove.    A  groove  that  marks  the  boundary  between  the  head 

and  thorax  of  some  crustaceans. 
Chela.     Large  claw  of  many  crustaceans;    also  applied  to  pincer-like 

claws  on  other  appendages. 
Che  late.     Bearing  pincer-like  claws. 

Chelicera.     One  of  the  anterior  pair  of  mouth  appendages  of  Arachnoidea. 
Chi  tin.     The  material  that  forms  the  outer  covering  of  insects  and  other 

animals. 

Chlorogog.    Excretory  cells  on  the  intestine  of  certain  annelids. 
Chlorophyl.    The  green  coloring-matter  of  plants. 
Choanocyte.    A  cell  provided  with  a  "collar." 
Chromatophore.     A  body  in  which  chlorophyl  is  lodged. 
Cilia.     Small  vibrating  appendages  of  cells. 
Cinclides.    Minute  openings  in  the  body-wall  of  coelenterates. 
Circular  canal.    Marginal  canal  of  a  medusa;  also  applied  to  the  water 

canal  that  surrounds  the  mouth  of  an  echinoderm. 
Circumferential  canal.    Marginal  canal  of  a  medusa. 
Cirrus.    A  soft  tactile  appendage. 
Cleavage.    The  act  of  cell  division. 
Clitellum.    The  thickened  glandular  region  on  an  earthworm  that  secretes 

the  egg  case. 
Cloaca.    A  space  that  receives  the  discharge  from  the  alimentary  canal 

and  kidneys,  and  frequently  from  other  organs. 
Cnidocil.    The  trigger  of  a  nematocyst. 
Ccelenteron.    The  internal  space  of  a  coelenterate. 
Coelom.     Body-cavity;    the  cavity  between  the  alimentary  canal  and 

body-wall. 

Coenosarc.     The  fleshy  continuation  of  a  hydroid  into  the  stalk. 
Collar-cell.    A  cell  provided  with  a  collar;  choanocyte. 
Colon.     Hinder  part  of  the  alimentary  canal. 

Columella.    Axis  around  which  the  spire  of  a  gastropod  shell  is  wound. 
Commensal.     Organisms  living  together  and  usually  partaking  of  the 

same  food. 

Commissure.    A  nerve  connecting  two  ganglia  of  a  pair. 
Compound  eye.    Eye  of  an  arthropod  that  is  composed  of  many  similar 

pieces,  called  omatidia. 
Connecting  canal.    The  canal  that  joins  the  tube  foot  to  the  radial  canal 

of  an  echinoderm. 


196  GLOSSARY. 

Connective.    A  nerve  connecting  two  ganglia  not  of  a  pair. 

Contractile  vesicle.     Contractile  excretory  organ  of  Protozoa. 

Copulation.     Sexual  union. 

Coxa.     Basal  segment  of  the  leg  of  an  insect. 

Coxopod.     Basal  segment  of  a  leg  of  a  crustacean. 

Crop.     An  enlargement  of  the  alimentary  canal  used  to  store  food. 

Crystalline  style.    A  transparent  rod  frequently  found  in  the  alimentary 

canal  of  lamellibranchs. 

Ctenophoral  row.    A  row  of  swimming  plates  on  a  ctenophore. 
Cuticle.     Outside  protective  covering. 
Cyst.    A  sac  or  pouch. 

Cystic  duct.    The  duct  that  leads  away  from  the  gall-bladder. 
Cysticercus.    A  stage  in  the  development  of  many  tapeworms. 

Dactylopod.     Last  segment,  seventh,  of  a  crustacean  leg. 
Dactylozobid.     Elongated  tentacle-like  zoftid  of  a  siphonophore. 
Denticle.     Small,  tooth-like  protuberance,  as  in  the  pharynx  of  some 

annelids. 
Dermal  branchiae.    Projections  on  the  surface  of  the  body  that  are  used 

for  respiration.     See  starfish. 
Development.    The  series  of  changes  that  lead  from  the  fertilized  egg  to 

the  mature  animal. 

Digestive  gland.    Any  gland  that  secretes  a  digestive  fluid. 
Dimorphism.    Two  distinct  forms  of  individuals  in  the  colony  or  species. 
Dioecious.     Sexes  in  two  separate  individuals. 
Directive   septa.    Those   placed   opposite   the   syphonoglyphes   of   an 

actinozoan. 

Disk.    The  central  portion  of  a  starfish. 
Dissepiment.    A  transverse  partition  in  an  annelid. 
Distal.     Remote  from  the  point  of  origin  or  attachment. 
Diverticulum.     An  out-pocketing  from  a  tube. 
Dorsal.    Back. 
Dorsal  lamina.     A  ciliated  ridge  on  the  dorsal  side  of  the  pharynx  of  an 

ascidian. 
Dorso-ventrally.    From  the  dorsal  to  the  ventral  position. 

Ectoderm.    The  outer  embryonic  layer. 
Ectoparasite.    A  parasite  on  the  outside  of  the  body. 
Ectoplasm.     Outer  layer  of  Amoeba  and  of  other  Protozoa. 
Efferent.     Going  away,  as  a  vessel  that  leads  away  from  an  organ. 
Elytra.    The  modified  fore- wings  of  a  beetle. 
Embryo.    An  immature  animal. 
Encyst.    To  inclose  in  a  cyst. 


GLOSSARY.  197 

Endoderm.    The  inner  embryonic  layer. 

Endoparasite.     A  parasite  inside  of  the  body. 

Endo-phragmal  skeleton.    Chitinous  plates  that  cover  the  nerve-chain 

and  ventral  blood-sinus  in  the  thorax  of  certain  crustaceans. 
Endoplasm.     Inner  portion  of  an  Amoeba  and  other  Protozoa. 
Endopod.    The  branch  of  a  biramous  appendage  of  an  arthropod  that  is 

nearest  the  mid-line  of  the  body. 
Endoskeleton.    An  internal  skeleton. 
Endostyle.    A  ciliated  groove  in  the  ventral  wall  of  the  pharynx  of  an 

ascidian. 

Ephyra.    An  embryonic  stage  of  Discomedusse. 
Epicardium.     A  hollow  process  from  the  pharynx  of  some  ascidians.     See 

Amarcecium. 

Epipharynx.     A  projection  from  the  roof  of  the  mouth  of  some  insects. 
Epiphysis.    A  plate  joined  to  the  base  of  the  alveolus  in  the  mouth-parts 

of  an  echinoid. 
Epipod.    A  membranous  projection  found  on  certain  crustacean  limbs, 

that  extends  into  the  gill  chamber. 

Episternum.    A  lateral  piece  next  to  the  sternum  of  arthropods. 
Epistome.    A  projection  above  the  mouth.     See  Pectinatella. 
Esophagus.    The  portion  of  the  alimentary  canal  that  leads  back  from 

the  mouth  or  pharynx. 

Euglenoid.     Similar  to  Euglena,  especially  in  movements. 
Ezopod.    The  branch  of  the  biramous  appendage  of  an  arthropod  that  is 

away  from  the  mid-line  of  the  body. 
Exoskeleton.    An  outer  covering,  as  a  shell. 
Exunibrella.     The  convex  side  of  a  medusa. 

Eye-spot.    A  pigment  spot  generally  supposed  to  be  associated  with  per- 
ception of  light. 

Femur.    The  third  segment  from  the  body  of  the  leg  of  an  insect. 

Fission.     A  method  of  asexual  reproduction  by  division. 

Flagellum.    An  elongated  vibratory  projection  of  a  cell. 

Flame-cell.    The  terminal  cell  of  one  of  the  excretory  tubes  of  the  Plathel- 

minthes. 

Foot.     A  locomotor  organ.     See  Venus. 
Funiculus.    A  strand  of  connective  tissue  that  connects  the  stomach  with 

the  body-wall  in  Polyzoa. 
Funnel.    The  tube  through  which  water  is  expelled  from  the  mantle 

chamber  by  cephalopods. 

Ganglion.    A  group  of  nerve  cells. 

Gastric  filament.    One  of  the  filaments  hi  the  stomach  of  Scyphozoa. 


198  GLOSSARY. 

Gastro-vascular.     Digestive  and  circulatory  in  function,  as  the  gastro- 

vascular  cavities  of  ccelenterates. 
Gastrozobid.     Feeding  individuals  of  hydroids. 
Genital  atrium.    A  space  receiving  the  genital  ducts.    See  Bdelloura. 
Genital  gland.    A  gonad. 
Genital  plate.     One  of  the  plates  through  which  the  gonads  open  in 

echinoderms. 
Genital  pore.    The  opening  in  the  genital  plate  or  other  external  opening 

of  a  gonoduct. 

Gill.    Aquatic  respiratory  organ. 

Gizzard.    A  muscular  triturating  division  of  the  alimentary  canal. 
Gonad.    A  generative  tissue,  a  germ  gland. 
Gonangium.     A  reproductive  individual   of  the  Leptomedusa3  that   is 

covered  by  a  gonotheca. 

Gonotheca.    The  transparent  covering  of  a  gonangium. 
Green  gland.     One  of  the  excretory  glands  of  certain  crustaceans. 
Gullet.    Esophagus;  the  tube  leading  back  from  the  mouth  or  pharynx. 
Gut.    Digestive  tube. 


Head.    The  anterior  division  of  the  body  of  higher  animals 

Hepatic  caecum.    Digestive  gland  of  a  starfish. 

Hermaphrodite.     With  male  and  female  sexual  organs. 

Holophytic.    The  nutrition  characteristic  of  plants. 

Holozoic.    The  nutrition  characteristic  of  animals. 

Homologous.     Of  similar  structure. 

Host.    The  animal  that  harbors  a  parasite. 

Hyaline.    Transparent,  glassy. 

Hydranth.     An  individual  of  a  hydroid  colony. 

Hydrocaulus.    The  stem  of  a  hydroid  colony. 

Hydrorhiza.     The  projections  by  which  hydroid  colonies  are  attached. 

Hydrotheca.    The  outer  secreted  covering  or  cup  of  a  hydranth. 

Hypobranchial  gland.  A  gland  near  the  gill  of  some  gastropods.  Some 
lamellibranchs  have  glands  that  bear  the  same  name. 

Hypodermis.  A  cellular  layer  that  lies  just  beneath  the  cuticle  of  anne- 
lids, arthropods  and  some  other  animals. 

Hypopharynx.  A  projection  borne  on  the  lower  side  of  the  pharynx  of 
some  insects. 

Hypophysis.    A  ventral  projection  from  the  brain  of  Chordata. 

Incurrent  canal.    A  canal  that  admits  water  to  a  sponge. 
Integument.     Skin;  outer  covering. 

Inter-ambulacral  area.  One  of  the  areas  of  an  echinoderm  that  lies 
between  adjacent  ambulacral  areas. 


GLOSSAEY.  199 

Inter-filamentar  junction.    A  connection  between  adjacent  filaments 

in  a  lamellibranch  gill. 
Inter-lamellar  junction.    A  connection  between  adjacent  lamellae  in  a 

lamellibranch  gill. 
Inter-radial  canals.    The  canals  of  a  medusa  that  lie  midway  between 

the  per-radial  canals. 

Intestine.     One  of  the  divisions  of  the  alimentary  canal. 
Introvert.     A  portion  that  will  turn  inward,  as  the  anterior  end  of 

Phascolosoma. 
Ischipod.    The  third  segment  of  a  typical  crustacean  leg. 

Kidney.    Frequently  applied  to  the  excretory  organ  of  an  invertebrate. 

Lab  rum.  The  appendages  that  form  the  lower  lip  of  insects  and  some 
other  arthropods. 

Lamella.  One  of  the  two  sides  that  form  a  lamellibranch  gill;  a  flat 
structure. 

Lamelliform.     Like  a  lamella;  thin  and  flat. 

Lamina.    A  thin  plate  or  a  scale. 

Lancet.    A  sharp  structure;  a  portion  of  the  sting  of  a  bee. 

Larva.    An  embryo;  a  stage  in  the  development  of  an  animal. 

Lateral.    At  or  toward  the  side. 

Ligament.  The  portion  that  unites  the  valves  of  a  clam  shell;  an  elastic 
connection. 

Lithite.     One  of  the  concretions  in  a  tentaculocyst  of  a  medusa. 

Liver.  Frequently  applied  to  the  largest  digestive  gland  of  an  inverte- 
brate. 

Lophophore.  The  disk  that  surrounds  the  mouth  and  bears  the  tentacles 
in  the  Molluscoida. 

Lorica.    The  transparent  covering  of  a  rotifer. 

Macronucleus.    The  larger  of  the  two  nuclei  of  certain  Protozoa. 
Madreporic  plate.    The  perforated  plate  through  which  the  water-vascular 

system  of  an  echinoderm  is  put  in  communication  with  the  sea- water. 
Mandible.     One  of  a  pair  of  mouth  appendages  of  an  arthropod. 
Mandibulate.     Possessing  mandibles. 
Mantle.     The  outer  fold  of  tissue  of  many  animals;  in  many  mollusks  and 

tunicates  it  secretes  a  protective  covering. 
Manubrium.     The  projection  at  the  end  of  which  the  mouth  is  situated  hi 

coelenterates. 
Marginal  lappets.    Small  flaps  of  tissue  near  the  sense  organs  of  Dis- 

comedusae. 
Mastaz.    A  division  of  the  alimentary  canal  of  a  rotifer. 


200  GLOSSAEY. 

Maxilla.     One  of  the  mouth  appendages  of  arthropods. 

Medusa.     Jelly-fish;  the  sexual  stage  of  certain  hydroids. 

Membranells.     Structures  formed  of  fused  cilia  found  in  some  Ciliata. 

Meropod.     The  fourth  segment  from  the  body  of  a  crustacean  leg. 

Mesenteric  filament.  The  modified  free  edge  of  a  mesentery  of  Actino- 
zoa. 

Mesentery.  A  membrane  that  supports  the  intestine;  one  of  the  par- 
titions of  Actinozoa. 

Mesoglea.  The  jelly-like  substance  that  separates  the  ectoderm  and 
endoderm  of  a  coelenterate. 

Metamere.     One  of  the  serial  body-segments  of  an  animal,  as  in  annelids. 

Metamorphosis.     A  change,  especially  in  form,  of  an  animal. 

Metapleural  fold.     One  of  a  pair  of  folds  on  the  sides  of  Amphioxus. 

Micronucleus.    The  smaller  of  the  two  nuclei  of  some  Protozoa. 

Moniliform.     Resembling  a  string  of  beads. 

Monoecious.     Sexes  united  in  one  individual. 

Mouth.    The  opening  through  which  food  is  taken. 

Myoneme.    A  contractile  fiber.     See  Vorticella. 

Nacre.    The  inner  layer  of  a  mollusk  shell. 
Nematocyst.    A  weapon  of  a  ccelenterate;  nettle  cell. 
Nephridiopore.     The  external  opening  of  a  nephridium. 
Nephrostome.     The  inner  opening  of  a  nephridium. 
Nerve  commissure.     A  nerve  connecting  two  ganglia  of  a  pair. 
Nerve  connective.     A  nerve  connecting  two  ganglia  not  of  a  pair. 
Nettle  cell.     Nematocyst;  a  weapon  of  a  ccelenterate. 
Neuropodium.     The  ventral  division  of  a  parapodium  of  an  annelid. 
Nidamental  gland.     An  accessory  reproductive  gland  possessed  by  some 

females,  especially  gastropods  and  cephalopods. 
Notochord.     A  supporting  structure  characteristic  of  Chordata. 
Notopodium.    The  dorsal  division  of  a  parapodium  of  an  annelid. 
Nuchal  groove.    A  groove  in  the  neck. 
Nucleus.     An  organ  of  a  cell. 

Odontophore.  A  special  structure  in  the  mouth  of  most  mollusca  except 
lameilibranchs.  The  name  is  applied  to  the  whole  structure,  cartilage, 
radula  and  muscles.  (It  is  used  by  some  authors  as  the  equivalent 
of  radula.) 

Ocellus.     A  simple  eye  of  an  arthropod. 

Ocular  plate.  A  plate  at  the  end  of  an  ambulacral  area  of  an  echino- 
derm. 

Olfactory  organ.     An  organ  to  distinguish  odors. 

Ooecium.     A  structure  in  Polyzoa  in  which  the  embryo  develops. 


GLOSSARY.  201 

Ootype.    The  space  in  flat- worms  where  the  eggs  are  supplied  with  shells. 
Operculum.    The  horny  lid  that  fits  into  the  aperture  of  the  shell  of  some 

gastropods. 

Oral.    The  mouth  side. 

Osculum.    The  opening  of  a  sponge  through  which  water  escapes. 
Osphradium.    A  supposed  sense  organ  of  Mollusca. 
Ossicle.     A  small  hard  plate. 
Ostium.    A  small  pore;    in  lamellibranchs  one  of  the  pores  in  the  gills 

through  which  water  is  passed. 

Otocyst.     A  sense  organ,  probably  static  in  function. 
Otolith.     A  hard  body  in  an  otocyst. 
Ovary.    A  female  sexual  gland. 

Oviducal  gland.     A  glandular  division  of  an  oviduct.     See  squid. 
Oviduct.     A  female  sexual  duct  that  leads  from  the  ovary. 
Ovipositor.    A  modified  portion  of  some  insects  that  is  used  in  depositing 

eggs. 
Ovum.    Female  germ  cell. 

Pal  Hal  line.  The  depression  in  the  shell  of  a  lamellibranch  that  is  caused 
by  the  attachment  of  pallial  muscles. 

Pa  Ilia  1  sinus.  The  indentation  in  the  pallial  line  of  some  lamellibranchs, 
caused  by  the  insertion  of  the  retractor  muscles  of  the  siphons. 

Pancreas.    A  digestive  gland. 

Papilla.     A  small  projection. 

Paragnatha.     Lamellae  behind  the  mandibles  of  some  Crustacea. 

Parapodium.     An  appendage  on  a  somite  of  an  annelid. 

Parenchyma.  A  soft  tissue;  that  which  fills  the  body-cavities  of  flat- 
worms. 

Pectine.     One  of  a  pair  of  appendages  of  scorpions. 

Pedicel  laria.  A  minute  pincer-like  organ  that  is  present  on  some 
echinoderms. 

Pedipalpi.    Appendages  of  Arachnoidea. 

Peduncle.     A  short  stalk. 

Pelagic.     Organisms  that  live  at  or  near  the  surface  of  the  water. 

Pen.     Vestigial  shell  of  a  cephalopod.     See  squid. 

Penis.     Male  intromittent  organ. 

Pericardium.     A  membrane  surrounding  the  heart. 

Periopod.     A  walking-leg  of  a  crustacean. 

Peri-pharyngeal  bands.  The  ciliated  bands  that  connect  the  endostyle 
and  dorsal  lamina  of  an  ascidian  around  the  mouth. 

Periproct.  The  region  around  the  anus  (especially  applied  to  the  echino- 
derms). 

Perisarc.    The  secreted  outer  covering  of  a  hydroid. 


202  GLOSSARY. 

Peristaltic.    The  motion  caused  by  the  successive  contraction  of  the 

muscle  fibers  in  the  walls  of  a  tube. 
Peristome.    The  region  around  the  mouth  (especially  applied  to  echino- 

derms). 

Peristomium.    The  somite  of  an  annelid  that  bears  the  mouth. 
Peritoneum.    The  membrane  that  lines  the  ccelom. 
Per-radial  canals.    The  canals  of  a  medusa  that  lie  opposite  the  corners 

of  the  mouth. 

Pharynx.    An  anterior  division  of  the  alimentary  canal. 
Planula.     A  young  coelenterate  embryo. 
Pleopod.    An  abdominal  appendage  of  a  crustacean. 
Pleurobranch.    A  gill  of  a  crustacean  that  is  borne  on  the  body-wall. 
Pleuron.     One  of  the  lateral  pieces  or  processes  of  a  somite  of  an  arthropod. 
Podobranch.     A  gill  of  a  crustacean  that  is  borne  on  the  basal  joint  of 

an  appendage. 

Polymorphism.    Many  distinct  forms  of  individuals. 
Polyp.    An  individual  of  a  hydroid  stage  of  a  coelenterate. 
Pore.    A  small  opening. 
Post-cava.    A  blood-vessel  that  leads  to  the  heart  from  the  posterior 

portion  of  the  body.    See  squid. 
Posterior.    Hinder;  anal  end. 
Pre-cava.    A  blood-vessel  that  leads  to  the  heart  from  the  anterior  end 

of  the  body.    See  squid. 
Primary  mesentery.    One  of  the  vertical  muscular  partitions  that  extends 

from  the  body-wall  to  the  esophagus  of  an  actinozoan. 
Proboscis.    Applied  to  various  tube-like  organs  around  the  head  that  are 

usually  capable  of  being  everted  or  protruded. 
Proglottid.    One  of  the  pieces  that  compose  the  body  of  a  cestode. 
Propod.    The  next  to  the  last  segment,  sixth,  of  a  typical   crustacean 

limb. 
Prosopyle.    One  of  the  pores  through  which  water  passes  from  an  incur- 

rent  to  a  radial  canal  of  a  sponge. 
Prostomium.    The  anterior  process  that  overhangs  the  mouth  of   an 

annelid. 

Prothorax.    Anterior  division  of  the  thorax  of  an  insect. 
Protomerite.    The  anterior  part  of  Gregarina. 
Protoplasm.     Cell  substance;  living  matter. 
Protopod.    The  first  two  segments  of  a  crustacean  limb  (the  protopod 

bears  the  exopod  and  endopod). 
Proximal.    Toward  the  origin  or  attachment. 
Pseudopodium.     One  of  the  changeable  protoplasmic  projections  of  the 

Sarcodina. 
Pyloric  division  of  stomach.    Posterior  or  second  division. 


GLOSSARY.  203 

Radial  symmetry.  With  the  parts  symmetrically  radiating  from  a  com- 
mon center. 

Radius.  One  of  the  parts  of  the  jaw  apparatus  of  an  echinoid;  from 
center  to  periphery. 

Radula.    The  flexible  membrane  of  an  odontophore  that  bears  the  teeth. 

Ray.     One  of  the  arms  of  a  starfish. 

Rectum.    The  posterior  division  of  the  alimentary  canal. 

Renal  organ.  An  organ  that  excretes  nitrogenous  wastes  and  other 
materials. 

Reservoir.    A  place  where  anything  is  stored;  the  poison  sac  of  a  bee. 

Respiratory  tree.     The  respiratory  mechanism  of  some  holothurians. 

Retractor  muscle.    A  muscle  that  withdraws  an  organ  or  portion. 

Rostrum.    The  anterior  spine  of  a  lobster  and  of  other  crustaceans. 

Rotula.     One  of  the  calcareous  pieces  of  the  jaw  of  an  echinoid. 

Rudimentary.  When  applied  to  adult  animals  means  permanently  unde- 
veloped; vestigial. 

Sagittal.    In  or  parallel  to  the  mesial  plane. 

Salivary  gland.    In  invertebrates  applied  to  any  gland  that  opens  into 

the  mouth  cavity. 
Scaphognathite.    The  epipod  of  the  second  maxilla  of  certain  Crustacea, 

that  is  used  in  baling  water. 
Schizopod.    A  biramus  Arthropod  appendage. 
Scolex.    Anterior  portion  of  the  tapeworm. 

Segment.    One  of  a  series  of  divisions  of  an  animal's  body  or  appendage. 
Segmentation.     Frequently  applied  to  the  cleavage  of  an  embryo. 
Seminal  receptacle.    A  sac  in  which  spermatozoa  are  stored. 
Seminal  vesicles.    The  sacs  that  inclose  the  testes  of  an  earthworm. 
Septum.    A  plate  that  divides  two  spaces.     See  Nereis. 
Sessile.     Fixed;  without  the  power  of  locomotion. 

Seta.    A  small  spine  of  an  annelid  that  is  usually  of  service  in  locomotion. 
Setigerous  gland.    A  gland  that  forms  setae. 
Sexual.    Of  or  pertaining  to  sex  or  sexes. 
Shell  gland.    A  gland  that  secretes  the  shell;   sometimes  applied  to  the 

kidneys  of  Entomostraca. 

Siphon.    Tubes  for  the  transmission  of  water  in  Mollusca. 
Somite.    Metamere;  one  of  the  serial  body-segments  of  an  animal  as  an 

annelid. 

Sperm.     Spermatozo6n;  male  reproductive  cell. 
Spennary.    Male  reproductive  body. 
Spennatheca.    A  seminal  receptacle,  used  for  storing  spermatozoa  hi  the 

female. 

Spermatophore.    A  specially  formed  package  that  contains  sperm. 
Spermatozoon.    Male  reproductive  cell. 


204  GLOSSARY. 

*/' 

Sperm-sphere.    A  mass  of  spermatozoa  in  the  earthworm. 

Spicules.    Minute  skeletal  bodies.     See  Grantia. 

Spinneret.     One  of  the  organs  by  means  of  which  a  spider  spins  its  thread. 

Spiracle.     Breathing  pore;  external  opening  of  the  tracheal  system. 

Spiral  valve.     The  complicated  posterior  portion  of  the  alimentary  canal 

of  a  shark. 
Spongin.    The  material  of  which  the  fibers  of  the  commercial  sponges 

are  composed. 

Spore.    A  small  reproductive  body  formed  asexually. 
Sporont.    The  detached  stage  of  Gregarina. 
Sporulation.    The  act  of  forming  spores. 
Stalk.    A  stem  or  a  peduncle. 

Statoblast.    Asexual  reproductive  body  of  certain  Polyzoa. 
Sternum.     The  ventral  covering  of  a  segment  of  an  arthropod. 
Stigma.    One  of  the  external  openings  of  the  trachea;  one  of  the  apertures 

in  the  pharynx  of  an  ascidian. 

Stolon.    An  extension  of  the  body-wall  from  which  buds  are  developed. 
Stomach.     A  division  of  the  alimentary  canal. 
Stomach-intestine.    A  division  of  the  alimentary  canal  that  functions 

as  both  stomach  and  intestine.     See  earthworm. 
Stomodaeum.    The  anterior  portion  of  the  alimentary  canal  that  is  ecto- 

dermal  in  origin. 

Stone  canal.     The  tube  that  leads  from  the  madreporic  plate  to  the  cir- 
cular water  canal  in  echinoderms. 
Stylet.     A  small  sharp  instrument. 
Sub-genital  pits.    The  pouches  adjacent  to  the  gonads  of  the  Discome- 

dusse,  on  the  subumbrellar  side. 
Sub -neural  gland.     A  glandular  body  in  ascidians. 
Sub-umbrella.     The  concave  (oral)  surface  of  a  medusa. 
Sulcus.    A  furrow  or  groove. 

Suture.     An  immovable  union  between  plates  or  ossicles. 
Swimmer et.     Pleopod;  an  abdominal  appendage  of  a  crustacean 
Swimming  plate.     One  of  the  swimming  organs  of  a  ctenophore. 
Synchronous.     Happening  at  the  same  time. 
Syphonoglyphe.     A  ciliated  groove  in  some  of  the  actinozoa. 
Systemic  heart.    A  heart  that  sends  blood  to  the  system.     See  squid. 

Tactile      Capable  of  feeling. 

Tarsus.    The  segmented  foot  of  an  insect. 

Telson.     Hinder  division  or  segment  of  a  crustacean. 

Tentacle.    An  elongated,  unsegmented  tactile  organ 

Tentaculocyst.     A  sense  organ  of  certain  medusae. 

Tergum.    The  dorsal  covering  of  a  segment  of  an  arthropod. 

Test.     Shell  of  an  echinoid;  tunic  of  an  ascidian. 


GLOSSAKY.  205 

Testis.    Male  genital  gland. 

Thorax.    The  body  division  of  arthropods  posterior  to  the  head. 

Tibia.    The  segment  of  the  leg  of  an  insect  that  is  between  the  femur  and 

tarsus. 

Trachea.    One  of  the  respiratory  tubes  of  certain  arthropods. 
Trichocyst.     An  infusorian  defensive  organ. 
Trivium.    The  three  rays  of  a  starfish  that  are  farthest  from  the  madre- 

poric  plate. 

Trochal  disk.    The  ciliated  disk  of  a  rotifer. 

Trochanter.    The  second  segment  from  the  body,  of  the  leg  of  an  insect. 
Trochophore.    An  embryo  of  certain  forms,  such  as  the  Annelida  and 

Mollusca. 

Tubercle.     A  small  knob-like  prominence. 
Tunic.     The  outer  covering  of  an  ascidian. 
Tympanum.     A  membrane  of  an  auditory  organ. 
Typhlosole.    A  longitudinal  ridge  in  the  intestine. 

Umbo.    The  raised  portion  of  the  valve  of  a  clam  shell  that  ends  in  the 

beak. 

Umbrella.    Applied  to  the  arched  portion  of  a  medusa. 
Uriniferous  tube.     One  of  the  tubes  of  a  kidney. 
Uropod.    One  of  the  pair  of  abdominal  appendages  that,  with  the  telson, 

form  the  tail-fin  of  a  crustacean. 
Uterus.    A  female  organ  in  which  young  develop. 


Vacuole,  contractile.    An  excretory  organ  of  Protozoa. 

Vacuole,  food.    A  temporary  space  in  Protozoa  in  which  food  is  digested. 

Vagina.     The  terminal  division  of  the  female  reproductive  duct. 

Vas  deferens.    The  duct  that  leads  away  from  the  testicle. 

Vas  efferens.  Sometimes  applied  to  one  of  the  divisions  of  the  male  repro- 
ductive duct  of  the  squid. 

Velum.     The  circular  muscular  membrane  of  a  medusa. 

Ventral.     Under  surface;  belly. 

Ventricle.    A  division  of  the  heart  which  forces  blood  to  the  body. 

Ventriculus.     A  division  of  the  alimentary  canal  of  an  insect. 

Vestibule.  A  depression  near  the  mouth  in  certain  Protozoa.  See  Vorti- 
cella. 

Vestigial.  An  organ  that  remains  undeveloped  and  has  no  function; 
rudimentary  as  applied  in  anatomy. 

Viscera.     Internal  organs  taken  collectively. 

Visceral  mass.  Applied  to  the  portion  of  a  mollusk  that  contains  stom- 
ach, intestine,  liver,  gonads,  etc. 


206  GLOSSARY. 

Vitellarium.    A  female  reproductive  gland  that  supplies  cells  to  be  used 

as  food  for  developing  embryos.     See  Bdelloura. 
Vitelline  glands.    Same  as  vitellarium. 

Water  tube.    One  of  the  tubes  between  the  lamellae  of  a  lamellibranch 

gill. 
Whorl.    A  turn  of  the  shell  of  a  gastropod. 

Yolk -mass.     A  mass  of  food  material  for  the  nourishment  of  an  embryo. 

Zoophyte.    An  animal  that  is  somewhat  plant-like  in  appearance. 
Zooid.     One  of  the  individuals  in  a  united  colony  of  animals.     See  Obelia 
and  Bugula. 


INDEX. 


References  to  directions  for  the  study  of  forms  are  indicated  by  the  use  of  boldface  type 
for  the  page  numbers. 


ACANTHOCEPHALA,  51 

Acarida,  135 
Acineta,  3 
Acmaea,  98 
Acrania,  174,  185 
Acridium,  136,  164 
Actiniaria,  23 
Actinophrys,  1,  6 
Actinosphaerium,  1,  6 
Actinozoa,  23,  34 
Adelochorda,  174 
^Eginopsis,  22 
JEolis,  98 
Agalena,  135 
Alcyonacea,  23 
Alcyonaria,  23,  36 
Alcyonium,  23 
Amarcecium,  174,  181 
Amoeba,  1,  4 
Amoebina,  1 
Amphineura,  97,  115 
Amphioxus,  174,  185 
Amphitrite,  78,  91 
Annelida,  78 
Anosia,  136 
Antedon,  61 
Anthomedusae,  22 
Antipatharia,  23 
Aphis,  136 
Apis,  137,  170 
Aplacophora,  98 
Aplysina,  17 


Apoda,  61 
Appendicularia,  174 
Appendix,  187 
Arachnida,  134 
Arachnoidea,  134,  158 
Araneida,  135 
Arbacia,  60 
Arcella,  1,  5 
Arcbi-annelida,  78 
Archi-chaetopoda,  78 
Arenicola,  78,  93 
Argonauta,  99 
Argulus,  133,  156 
Armata,  78 
Arthostraca,  134 
Articulata,  56 
Ascaris,  51 
Ascidiacea,  174 
Ascidian,  176 
Aspidobranchia,  98 
Asterias,  60,  61 
Asteroidea,  60,  61 
Astrangia,  23,  36 
Astropecten,  60 
Astrophyton,  60 
Aurelia,  23,  32 
Autolytus,  78,  88 

BALANOGLOSSUS,  174,  175 
Balanus,  133 
Barnacle,  156 
Bdelloura,  39,  41 
207 


208 


INDEX. 


Beach-flea,  151 
Bee,  170 
Beetle,  166 
Benacus,  136 
Beroe,  24 
Beroida,  24 
Blue  crab,  144 
Botryllus,  174,  180 
Brachionus,  54 
Brachiopoda,  56,  58 
Branchipus,  133,  153 
Buccinum,  98 
Bug,  167 
Bugula,  56 
Bulla,  98 
Buthus,  134,  159 
Butterfly,  167,  171 

CALCAEEA,  17 
Callinectes,  134,  144 
Cambarus,  134,  137 
Campanularia,  26,  28 
Cancer,  134 
Caprella,  134,  153 
Caryophyllseus,  39 
Centipede,  163 
Cephalopoda,  98,  124 
Ceratium,  2,  9 
Cerebratulus,  40,  49 
Cestida,  24 
Cestoda,  39,  46 
Cestus,  24 
ChaBtognatha,  51 
Chsetopleura,  98,  115 
Chaetopoda,  78,  79 
Chaetopterus,  78,  90 
Chalina,  17,  21 
Charybdea,  23 
Chelifer,  134 
Chilopoda,  135 
Chiton,  98,  115 
Chordata,  174 
Cicada,  136 


Ciliata,  3 
Cirripathes,  23 
Cirripedia,  133 
Cistenides,  78,  92 
Clam,  99,  112,  113 
Clam-worm,  79 
Clathrulina,  1,  7 
Clava,  29 
Clearing,  189 
Clepsine,  79 
Cliona,  17,  21 
Clymenella,  78,  92 
Clypeastroidea,  60 
Coccidiidia,  2 
Coccidium,  2 
Ccelenterata,  22 
Coleoptera,  136 
Copepoda,  133 
Corticella,  17 
Crab,  144,  148 
Crab,  horseshoe,  158 
Crangon,  134 
Craniata,  174 
Crayfish,  137 
Crepidula,  98,  11, 
Crinoidea,  61 
Crossobothrium,  39,  46 
Crustacea,  133,  137 
Cryptozonia,  60 
Ctenophora,  23,  37 
Cubomedusse,  23 
Culex,  136 
Cumacea,  134 
Cumingia,  99 
Cuspidaria,  97 
Cyclops,  133,  155 
Cydippida,  24 
Cypris,  133 
Cystoflagellidia,  2 

DAPHNIA,  133,  154 
Decapoda  (Arthropoda),  134 
(Mollusca),  99 


INDEX. 


209 


Dehydrating,  188 
Deiopea,  24 
Demospongiae,  17, 
Dentalium,  98 
Dermacentor,  135 
Diastylis,  134 
Dibranchiata,  98 
Dictyonina,  17 
Difflugia,  1,  5 
Digenetica,  39 
Dinoflagellidia,  2 
Dinophilea,  54 
Diopatra,  78,  90 
Diplopoda,  136 
Diptera,  136 
Discomedusae,  23 
Distomum,  44 
Dolichoglossus,  174,  175 
Doliolum,  174 
Dondersia,  98 
Doryphora,  136 

EARTHWORM,  82 
Earwig,  163 
Echinarachnius,  60 
Echinodennata,  60 
Echinoidea,  60,  68 
Echinorhynchus,  51 
Echiurus,  78 
Ectoprocta,  56 
Elasipoda,  61 
Endoprocta,  56 
Ensis,  99,  113 
Entomostrica,  133 
Epeira,  135,  160 
Ephelota,  3 
Eudendrium,  29 
Euglena,  2,  7 
Eulamellibranchia,  97 
Eupagurus,  134,  148 
Euplectella,  17 
Euplotes,  3,  14,  15 
Eurete,  17 
14 


Euryalida,  60 
Euspongia,  17 
Euthyneura,  98 

FAIRY  shrimp,  153 
Favia,  36 
Filibranchia,  97 
Fish-louse,  156 
Fixing,  187 
Flagellidia,  1 
Fly,  167,  171 
Foraminifera,  1,  5 
Fresh-water  mussel,  99 

polyp,  24 
Fulgur,  98,  116 

GALEODES,  134 
Gammarus,  134 
Gastropoda,  98,  116 
Gastrotricha,  54 
Gephyrea,  78,  95 
Gigantostraca,  134 
Globigerina,  1 
Glossary,  193 
Glossiphonia,  79 
Gnathobdellida,  79 
Gonionemus,  22,  29 
Goose-barnacle,  156 
Gordius,  51 
Gorgonacea,  23 
Gorgonia,  23,  36 
Grantia,  17,  18 
Grasshopper,  164 
Gregarina,  2,  10 
Gregarinida,  2 
Gryllus,  136 
Gymnolsemata,  56 

H^EMATOLCECHUS,  44 

HsBmosporidiida,  2 
Haliotus,  98 
Halteria,  3 
Heliozoa,  1 


210 


INDEX. 


Helix,  98 
Hemiptera,  136 
Hermit  crab,  148 
Heteroccela,  17 
Heterotrichida,  3 
Hexactinellida,  17 
Hexagenia,  136 
Hippa,  134,  148 
Hirudinea,  78 
Hirudo,  79 

Holothuroidea,  60,  74 
Holotrichida,  3 
Homarus,  134,  137 
Homocoela,  17 
Honey  bee,  170 
Horseshoe  crab,  158 
Hydra,  22,  24 
Hydractinia,  29 
Hydrocorallina,  22,  31 
Hydroides,  78,  94 
Hydrozoa,  22,  24 
Hymenoptera,  137 
Hypotrichida,  3 

INARTICULATA,  56 
Inermia,  78 
Infusoria,  3,  11 
Insecta,  136,  164 

JULUS,  136,  164 
KERATOSA,  17 

LACHNOSTERNA,  136 
Lamellibranchiata,  97,  99 
Larvacea,  174 
Lecythium,  1 
Lepas,  133,  156 
Lepidonotus,  78,  89 
Lepidoptera,  136 
Lepisma,  136 
Leptolinae,  22 
Leptomedusse,  22 


Leptoplana,  39 
Leucosolenia,  17,  21 
Libellula,  136 
Lichnophora,  3,  14 
Limax,  98 
Limnsea,  98 
Limulus,  134,  158 
Lingula,  56 
Lithobius,  135,  163 
Lobata,  24 
Lobster,  137 
Loligo,  99,  124 
Long  clam,  112 
Loxosoma,  56 
Lumbricus,  78,  82 
Lyssacina,  17 

MADREPORARIA,  23,  36 
Malacostraca,  133 
Margelis,  29 
Mastigamoeba,  2 
Mastigophora,  1,  7 
Meandrina,  23,  36 
Meckelia,  49 
Melocerta,  54 
Membranipora,  56 
Metridium,  23,  34 
Microsporidia,  2 
Microstomum,  39 
Millepora,  22,  31 
Mnemiopsis,  24,  37 
Modiola,  97,  109 
Molgula,  174,  176 
Mollusca,  97 
Molluscoida,  56 
Monaxonida,  17 
Monogenetica,  39 
Monozoa,  39 
Mosquito,  171 
Mounting,  189 
Musca,  136 
Mussel,  109 
Mya,  97,  112 


INDEX. 


211 


Myriapoda,  135,  163 
Mysis,  133,  151 
Mytilus,  97,  99,  109 
Myxidium,  2 
Myxospongida,  17 
Myxosporidiida,  2 
Myzostoma,  78 
Myzostomida,  78 

NARCOMEDUS^J,  22 
Nautilus,  99,  132 
Nebalia,  133 
Nemathelminthes,  51 
Nematoda,  51 
Nemertinea,  40,  49 
Neo-crinoidea,  61 
Neomenia,  98 
Neosporidia,  2 
Nereis,  78,  79 
Neuroptera,  136 
Noctiluca,  2,  9 
Nucula,  97 

OBELIA,  22,  26 
Octopoda,  99 
Octopus,  99,  132 
Oligochseta,  78 
Oniscus,  152 
Onychophora,  135 
Ophiura,  60,  67 
Ophiurida,  60 
Ophiuroidea,  60,  67 
Opisthobranchia,  98 
Orbicella,  23,  36 
Orthoptera,  136 
Oscarella,  17 
Ostracoda,  133 
Ostrea,  97,  111 
Oxytricha,  3,  14 
Oyster,  111 

PARAM^ECIUM,  3, 11 
Parypha,  22,  28 


Patella,  98 
Pauropoda,  136 
Pauropus,  136 
Pecten,  97,  103,  110 
Pectinatella,  56,  58 
Pectinibranchia,  98 
Pedata,  61 
Pedicellina,  56 
Pediculus,  136 
Pedipalpida,  134 
Pennaria,  29 
Pennatula,  23 
Pennatulacea,  23 
Pentacrinus,  61 
Peranema,  2,  7 
Pericolpa,  23 
Peridium,  2 
Peripatus,  135 
Periplaneta,  136 
Peromedusse,  23 
Perophora,  174,  180 
Petasus,  22 
Phacus,  7 
Thalangida,  135 
Phalangium,  135 
Phanerozonia,  60 
Phascolosoma,  78,  95 
Philampelus,  136 
Phoronida,  56 
Phoronis,  56 
Phoxichilidium,  135,  162 
Phrynus,  134 
Phylactolaemata,  56 
Phyllapoda,  133 
Phyllocarida,  133 
Physalia,  22,  31 
Placophora,  97 
Planaria,  39,  40 
Planocera,  39,  43 
Plasmodium,  2 
Platyhelminthes,  39 
Platysamia,  136 
Pleurobrachia,  24 


212 


INDEX. 


Pleurotricha,  3,  14 
Plumatella,  56,  58 
Plumularia,  28 
Podophyra,  3 
Polychaeta,  78 
Polychoerus,  39 
Polycladida,  39 
Polygordius,  78 
Polystomum,  39 
Polyzoa  (Cestoda),  39 

(Molluscoida),  56 
PontobdeUa,  79 
Porcellio,  134,  152 
Porifera,  17 
Preparations,  187 
Prorodon,  3 
Proterospongia,  2 
Protobranchia,  97 
Protozoa,  1 

method  for  preparing,  191 
Pseudo-lamellibranchia,  97 
Pseudo-scorpionida,  134 
Pulmonata,  98 
Pycnogonidia,  135,  162 

QUAHOQ,  99 

RADIOLABIA,  1 
Razor-shell  clam,  113 
Regularia,  60 
Renilla,  23,  36 
Rhabdocoelida,  39 
Rhizopoda,  1,  4 
Rhynchobdellida,  79 
Rotifer,  54 
Rotifera,  54 
Round-web  spider,  160 

SABELLA,  78,  93 
Saccocirrus,  78 
Sagartia,  23 
Sagitta,  51 
Salpa,  174,  183 


Sand  mole,  148 
Sarcocystis,  3 
Sarcoptes,  135 
Sarcosporidia,  3 
Scallop,  110 
Scaphopoda,  98 
Schizopoda,  133 
Scolopendrella,  135 
Scorpion,  159 
Scorpionida,  134 
Scyphozoa,  22,  32 
Sea-anemone,  34 
Sea-cucumber,  74 
Sea-pork,  181 
Sea-urchin,  68 
Sections,  190 
Sepia,  99 
Septibranchia,  97 
Serpent-star,  67 
Sertularia,  28  j 
Shrimp  (fairy),  153 
Silenia,  97 

Siphonophora,  22,  31 
Sminthurus,  136 
Solenomya,  112 
Solpugida,  134 
Sow-bug,  152 
Spatangoidea,  60 
Spider,  160 
Spirorbis,  78,  94 
Spirostomum,  3,  12 
Spirula,  99 
Spongilla,  17,  21 
Sporozoa,  2,  10 
Squid,  124 
Squilla,  134,  149 
Staining,  188 
Starfish,  61 
Stauromedusae,  23 
Stentor,  3 
Stomatopoda,  134 
Streptoneura,  98 
Strongylocentrotus,  60,  68, 


INDEX. 


213 


Stylaster,  31 
Stylochus,  39 
Stylonychia,  3,  14 
Suberites,  17 
Sycotypus,  116 
Symphyla,  135 
Synaptula,  61 
Syncoelidium,  39,  41 
Syzygies,  10 

TABANUS,  136 
TaBnia,  39 

Talorchestia,  134,  151 
Telosporidia,  2 
Terebratulina,  56,  58 
Termes,  136 
Tessera,  23 
Tetrabranchiata,  99 
Tetrastemma,  40,  49 
Tetraxonida,  17 
Thaliacea,  174 
ThallassicoUa,  1 
Thousand-legs,  164 
Thyone,  61,  74 
Thysanura,  136 
Trachelomonas,  7 
Trachydermon,  98 
Trachylinae,  22 


Trematoda,  39,  44 
Trichina,  51,  52 
Tricladida,  39 
Tritia,  116 
Trochehninthes,  54 
Trypanosoma,  2 
Tubifex,  78 
Tubipora,  23 
Tunicate,  176 
Turbellaria,  39,  40 

UNIO,  97,  99 
Urochorda,  174,  175 

VENUS,  97,  99 
Vertebrata,  174 
Vespa,  137 
Volvox,  8 
Vorticella,  3,  13 

WASHING,  188 
Water-flea,  155 

YOLDIA,  97,  99,  107 

ZOANTHARIA,  23 

Zodthamnium,  3 


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Saunders*  College  Text-Books 


Immediate  Care  of  the  Injured.  By  ALBERT  S.  MORROW,  M.  D., 
Adjunct  Professor  of  Surgery,  New  York  Polyclinic.  Octavo  of 
360  pages,  242  illustrations.  Cloth,  $2.50  net.  Second  Edition. 

Dr.  Morrow's  book  tells  you  just  what  to  do  in  any  emergency,  and  it 
is  illustrated  in  such  a  practical  way  taat  the  idea  is  caught  at  once. 
There  are  chapters  on  bandaging,  practical  remedies,  first-aid  outfit, 
hypodermic  injections,  antiseptics  and  disinfectants,  accidents  and 
emergencies,  hemorrhages,  inflammation,  contusions  and  wounds,  burns 
and  scalds,  the  injurious  effects  of  cold,  fractures  and  dislocations, 
sprains,  removal  of  foreign  bodies  from  the  eye,  ear,  nose,  etc.,  poisons, 
and  their  antidotes.  There  is  no  book  better  adapted  to  first-aid  class 
work. 

Health :  "  Here  is  a  book  that  should  find  a  place  in  every  workshop 
and  factory  and  should  be  made  a  text-book  in  our  schools." 


American  Illustrated  Medical  Dictionary.  By  W.A.NEWMAN 
BORLAND,  M.  D.,  Member  of  Committee  on  Nomenclature  and 
Classification  of  Diseases,  American  Medical  Association.  Octavo 
of  1107  pages,  with  323  illustrations,  119  in  colors.  Flexible 
leather,  $4.50  net ;  thumb  indexed,  $5.00  net.  Seventh  Edition 

If  you  want  an  unabridged  medical  dictionary,  this  is  the  one  you 
want.  It  is  down  to  the  minute;  its  definitions  are  concise,  yet  accu- 
rate and  clear;  it  is  extremely  easy  to  consult;  it  defines  all  the  newest 
terms  in  medicine  and  the  allied  subjects;  it  is  profusely  illustrated. 
This  new  edition  alone  defines  over  5000  new  terms  not  defined  in  any 
other  medical  dictionary— bar  none.  There  is  no  other  medical  dic- 
tionary that  will  meet  your  needs  as  well  as  The  American  Illustrated. 
Why  not  then  get  the  best  ?  -A  ;.'< 

John  B.  Murphy,  M.  D.,  Northwestern  University:  "  It  is  unquestion- 
ably the  best  lexicon  on  medical  topics  in  the  English  language,  and, 
with  all  that,  it  is  so  compact  for  ready  reference." 

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Renewed  books  are  subject  to  immediate  recall. 


DEC    21955 

JAN  5     1961 

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JAN  4     1903 

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